Speaking exclusively to DS, the 22-year-old actor said that the Girls Aloud star had done a "great job" in the Dominic Savage drama.
"I wasn't in her scenes but when we were shooting, we had the same location so I saw her and she's brilliant in it," he admitted.
"I'm not one to say whether she has or she hasn't [done well], but to me it looks like she's done a great job. She trained as an actress anyway, so she's not completely new to it. She knows what she's doing, in a way. She definitely got it, from what I could see."
Freefall airs tomorrow at 9pm on BBC Two.
> Click here to read our full interview with Alfie Allen