Ali moves into Brook Cottage with her children Sean and Amelia, looking for a fresh start having recently left her husband for another woman. However, there's bound to be fireworks ahead in the family as she plans to move her girlfriend Ruby (ex-Bad Girls actress Alicya Eyo) in too - which leaves Sean horrified.
Here, Kelli chats about joining Emmerdale and what viewers can expect from Ali.
How would you describe Ali?
"She's feisty and she will do anything for her kids. She has left her husband for a woman, but she doesn't have any issues about having made that decision. What she is dealing with are the dynamics of the family and how the decision affects the family.
"She just wants to find a way for them all to get on together, including with her sister Rachel. For Ali, everything is about keeping the family together at the moment."
Why has she decided to move to Emmerdale?
"Ali has left her husband of 15 years, who is apparently a good man and a great father, and she met Ruby. She has never been in a relationship with a woman before and she never planned to become a lesbian, but she met Ruby and has fallen in love and this is about a fresh start for all of them.
"There are no doubts in Ali's mind where Ruby is concerned - she didn't take the decision to leave her husband and split up the family lightly. She's fallen in love and she is 100% committed to Ruby. Ruby might occasionally worry this is a phase for Ali or a flash in the pan, but it absolutely isn't.
"They are from a council estate in Hotten but Rachel tells them about the village and Brook Cottage being available. Rachel convinces Ali to take it and start a new life in Emmerdale."
Why have we seen Rachel looking after the children?
"The kids' dad works away a lot because he's a truck driver and I think because it's early days with Ali and Ruby, they've made the decision to be together but don't want Ruby to be too full-on with the kids initially. So the kids have been spending a lot of time with Rachel in the village. I think their plan is to gradually integrate Ruby into the family."
Why hasn't Ali told Sean that they are moving to the village?
"She thinks Sean would do a runner. They are obviously having issues with him already and that would probably be the icing on the cake. If she asks him if he wants to move to the village she knows he'll say no, so why bother asking? She hopes to hold off the grief for a bit longer!
"The anger he's got has been building because not only has his mum left his dad, but she's left him for a woman. So he's probably getting loads of stick off his mates at school and that's why he's bunking off school. He's bound to rebel. He's 14 and he's angry!"
On moving day, Amelia is involved in an accident. Can you talk us through what happens?
"While they are moving furniture in, there is a lot going on and they take their eyes off her. Carl and Cameron are messing about in their cars trying to get at each other, and Amelia steps out into the road as Carl is reversing.
"Luckily, Sam grabs her but she dislocates her shoulder. So Ali reacts by punching Carl in the face. I don't think she is necessarily a violent person but when it comes to her kids, that is what she'll do, whatever it takes to protect them. So we can expect a few more punches, I hope so anyway!"
Do you think Ali will settle in the village, and is it going to be what she's hoping it will be?
"I don't think it's going to be initially. I think for a while she will question whether she has made the right decision, due to Sean's reaction. She knows it's the right decision for herself, but she'll question if it's the right thing for the family. I think Ali will expect a reaction to her and Ruby's relationship in such a small village, but there is no major statement.
"Slowly but surely, everyone sort of twigs that they're a couple so we'll see how that goes. Sean is the only one who's got the issue at the moment, and her ex-husband of course. He is set to turn up on the doorstep, but Ali just wants the life that she's chosen to have now and doesn't want anyone messing it up."
Who do you think Ali will cross paths with in the village?
"She has a run-in straight away with Nicola, but who doesn't? I'd like her to get really palled-up with Edna, because you often find the most random people end up becoming really good friends and I think Edna could do with a best bud. I could be the one who goes round for a cup of tea and educates her a little bit!"
How did the part come about for you?
"In this job, whenever you get a job, the chances are you're going to be away from home, so when the phone call came about the part, everyone was telling me, 'This is perfect for you'. It was all a bit too good to be true to start with, so I didn't build my hopes up.
"Alicya and I had different partners in the screen test and I was so sure she would get the part and because she had a different partner, I thought that was it for me. But when I got it, I was just over the moon. I'm from Leeds and live just ten minutes from the studio and Emmerdale is just an institution, so to get a job here is just amazing.
"It's a lot more subtle than some of the other soaps. Obviously there is big drama, but they do it so well. Whatever Emmerdale does, they always do very, very well. When my agent called, I was running up and down the street and ringing my mum who was screaming down the phone and crying. She says I've got to bring her to work to meet Cain. I think she'll be stalking him!"
How was your first day on set?
"I was absolutely petrified and my first scene was in The Woolpack, so I was really worried and thrown in at the deep end. I was hoping no-one would make a fuss so I could sneak on and get the scene done, but I had worked with the director before so he made this big announcement on set and I just wanted to die! Everyone was so lovely, though, and coming over to tell me about their first days. Everyone has been so welcoming."
> Emmerdale announces new characters Ali and Ruby
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> Read all the latest Emmerdale spoilers and news
Ali Spencer arrives on-screen on Monday, October 17 and Ruby Haswell arrives on Thursday, October 20.