The character you are talking about is Lily. And no, I think you're wrong. I've already seen this movie 3 times to pretty much know that your assumption is incorrect, but I get why you think that.
I know it is a figment of her imagination but what I was saying is that to Nina, it was real and I bought her belief of it being real. What I mean is, I was right there with her for every step of her breakdown. It wasn't real but it felt real. I'm not getting my point across very well lol
I know the sex and everything was in her head, I don't think it actually happened, but as I was watching I was right there with Nina...Am I making sense?