Wadia worked alongside her composer husband Raiomond Mirza on the production, which stars Sean Pertwee, Craig Conway, Kierston Wareing and Martin Compston.
Over in soapland, meanwhile, the star's EastEnders character Zainab Masood has endured a turbulent year due to the manipulations of her ex-husband Yusef Khan - a situation which looks likely to escalate in the build-up to Christmas.
Here, Nina chats to Digital Spy about Four and her current EastEnders storylines.
How did your new film project Four come about?
"Myself and my husband Raiomond Mirza have a film production company called Oh My! Productions, and we've had that for easily over ten years. We've wanted to do something interesting with the production company for such a long time, but because we've both been working on other projects it's not happened until now.
"A couple of years ago, the script for Four landed on our desk from a writer called Paul Chronnell, and we thought it was absolutely fantastic. It was a concise piece that we knew we could put together, as we'd been hoping to make an indie film. Before we knew it, we were working on our first film project together."
What kind of a budget did you have for the film?
"It started off on a low budget, but then it expanded rather rapidly! If you ever make your first film, you'll find out that everything goes out of control due to unforeseen circumstances. So we've learned a few lessons from this one, but it's been an adventure and at least now we're prepared for our next movie."
What was it like to work so closely with your husband on a project?
"It was difficult sometimes - people say you should never work with your partner! But on the positive side, it was very exciting and it was like having our third child, because we did look at it as our baby. My husband did most of the legwork, because EastEnders was taking over my life, so he made a joke that I was the silent producer but I wasn't very silent!"
Was it difficult to fit the film in with your EastEnders commitments?
"Well, we filmed it in the coldest February that England has ever known, in a warehouse in West London. The way it would work was that I would go to work at EastEnders, come home around 7pm and look after the kids while my husband went on the set, as it was mostly night shoots. He'd then work until 7am in the morning and then we'd swap over again! So it was very, very tough.
"The whole process took about two years, from receiving the script to having the premiere later this month, but from what we've been told that's actually quite quick for a movie. The film goes on general release on October 21."
What is the day-to-day role of an executive producer on a film?
"From morning to night, it's being at the beck and call of everything that needs to be done to make the film work. That includes all of the preparation work, working with the line producer, and getting the casting done. You have to be on top of everyone's needs and make sure that everybody's happy all the time.
"My husband was also the composer of the film, so for him it was quite a learning experience too. For both of us, we have jobs in the business but not in producing, so we had a lot to learn along the way."
What can you tell us about the actual storyline of Four?
"This is the dangerous thing about this film, as I can't tell you too much! It's about a relationship that's gone wrong, and the games that people play in trying to sort out what should be a very private, intimate thing. But I can't tell you much more than that, because there's a fabulous twist in it! If I say anything more than that, it'll give it away. All I can say is that if you want to see class acting and a great little script, go and see it. It's very, very clever."
Do you think Four would appeal to an everyday EastEnders fan?
"Yes, I do. We've been quite lucky, as we've been given a 15 certificate. I think the film will appeal to people who enjoy a bit of darkness in their lives. Having said that, it is supposed to be a dark comedy and there's a lot of humour in the dialogue, especially between the male characters. I think it would appeal quite well to the EastEnders audience."
Are the four main characters the only ones who feature in the movie?
"Yes, and the reason for that is because we were on quite a low budget for our first film, we had to keep the cast small - especially to make sure that we got the cast that we wanted. We also had to keep the locations quite concise. But it's quality and not quantity that matters. I promise you that these four characters really do hold your attention for the whole hour and a half. It really allowed each cast member to come into their own."
Have your EastEnders colleagues been supporting you with this project?
"Yes they have, and I cannot thank them enough. It's not just the actors but the whole team - everyone has been so incredibly supportive. I actually want to thank them for their support, because it's like a big family on EastEnders."
There's been lots of twists and turns for the Masoods on EastEnders this year. Have you enjoyed the recent storylines?
"Very much so! It's so nice to be able to sink your teeth into something, and I'm really going to enjoy this wave as much as I can, because I know that there'll have to be a downtime after it. It's nice to have done the comedy, but now take Zainab to quite a dark place. Hopefully she'll come out the other end."
What's it like to have Preeya Kalidas back on set playing Amira at the moment?
"It's so fun. We always tease Preeya about being the diva on set, but she's great as she takes it really, really well and she can give it back too! (Laughs) It's such a nice atmosphere between us all on set, and we actually have to get told off by the director because we laugh so much!"
From what we've heard, the current storyline with Yusef will be running until the end of the year. Are there more shocks and surprises to come?
"Oh gosh, there's definitely more shocks and surprises to come for Zainab! The scripts seem to get darker and darker each time, and every time I open a new one, my jaw drops. The coolest thing is that I've just received scripts for two weeks prior to Christmas, and those scripts have already shocked the life out of me. So goodness knows what Christmas itself will bring!
"The scripts are page-turners. When you get those scripts where you can't wait to see what comes next, that's when you know that you've got something special in your hands. I'm literally thinking, 'Oh my God, oh my God, what's going to happen next?'"
In all the plotting and scheming, what do you think Yusef's main intention is? Does he want a future with Zainab or does he just want revenge?
"I think that's the clever thing about the way Ace [Bhatti] plays Yusef - you never really know! Sometimes when I'm playing the scenes I'm not quite sure, and I only figure it out when I watch them back. I think what Ace does is really brilliant - it unnerves me both as an actor and as a character. I personally think that somewhere in there, Yusef has a love for Zainab, but I think his primary intent has to be revenge. That's what I think as Nina, but not as Zainab. I think Zainab falls in love with him, and she actually thinks that they could love each other."
Zainab and Syed seem to be on better terms these days…
"They are, but there's always an edge with them, no matter how close they get. There often seem to be scenes where Zainab is crying with him, or if they're laughing, it only seems to last for about 30 seconds!"
If Christian and Syed do get married, do you think Zainab would be there on the day?
"At this point, definitely not! I think at the moment, Zainab can just about accept Syed and Christian being together, but actually getting married is a whole different ball game. She even says in a few scripts, 'Never' and 'Over my dead body'!"
Why do you think the Masoods have proved such a success with EastEnders fans?
"I think it's that we get on really, really well. We're all great friends, and we're very tolerant of each other and our little quirks. We know that working as a team is what produces the best work, and if we have any suggestions or ideas, we all respond to each other really well."
> Read all the latest EastEnders spoilers and news
Nina Wadia's new film Four goes on general release in cinemas from October 21.