Cave plays Biddy in the new reworking of Charles Dickens's novel, which reunites her with Harry Potter colleagues Ralph Fiennes and Helena Bonham-Carter.
"The Harry Potter thing for Great Expectations was utterly irrelevant," Cave told Digital Spy.
"People like Helena Bonham-Carter and Ralph Fiennes, they won't remember you. So even if you were like, 'Hey, I was Lavender Brown', they'll be like, 'Er...'."
She added: "You make a connection on a day-to-day basis. We were in a make-up trailer and it was just me, Helena and Ralph, and that would never have happened on Harry Potter because comparatively it's a tiny production. And it was thrilling!
"It was so exciting to be in the same place as them, but it was also such a different film, so Ralph was playing Magwitch, a really dark and violent character. He'd just sit there and look psychotic, and then Helena was just so free, and... I just adore her."
Cave said: "It's nothing like the BBC adaptation that was on TV, because that was totally different.
"It's beautiful. The colours and everything look stunning. The central journey is Pip (Jeremy Irvine) in this one. His journey to become a man and have these great expectations. That's the focus."
She continued: "Mike is brilliant as a director.... he's an amazing editor. He's chopped down this literary classic into probably under two hours. There's nothing in there that's gratuitous.
"I really respect that because we could sit there through a three-hour film - I'd be in it more, great - but it's not what it's about. It's about making a good film, and I think he's made a really good film."
Jessie Cave brings her show Bookworm to Underbelly Cowgate at the Edinburgh Fringe August 4 to 26 (not 13). Tickets are available now (£9-£10).