She knows the difference. She grew up reading the comics. Psylocke was her favorite character. She even had to explain to the director about the character:
"I was like, you know, there is that storyline, and I was really big  about staying so true to Psylocke. In fact, I was like, Um, shes  actually Psylocke because of the alien that took her body. She took on  the name Psylocke because that was the aliens name. And she becomes  Psylocke after the Apocalypse, but theyre like, Stop talking  (laughs). I mean, I literally wrote a paragraph and at the end of it was  like, Do you guys want to fire me now. Am I too nerdy?
I think my first thought [when I saw the costume] was it has to be  purple, because we were going up against time and making it. It was  black at first because thats the way tothe latex is in black and all  the armor is in black and its just easier, but I was like, Youve got  to make it purple. That was kind of my first thought when I saw myself  in the costume, which was in Photoshop.
Psylocke is telepathic and telekinetic. In the movie, we see her being a  telekinetic. We dont see her being telepathic. Its a decision [we  made] because this is the first time weve really been able to see the  character of Psylocke and have her really, truly exist in the movie. I  talked about it with Simon Kinberg. Theres just so much going on,  especially with Apocalypses power, and then trying to take on all of  the X-Men. When you are telephatic, I feel that its a power that you  want to hold close to your chest. Its a card that you dont want a lot  of people to know about because its so much more powerful when people  dont know that you have this power.
Some of my fight scenes that I have, Im able to go after them quickly  because Im already assessing what theyre going to do but they dont  know that I have that ability. We create the sword and some other  things, but the telepathy is incorporated in our decisions and  everything that were doing. My character might ask a question but she  already knows the answer, but weve already thought about that. Its  more of something I think for the fans to be able to know like, Oh,  thats a cool moment because you can kind of see that youre one step  ahead with her."
I think if Psylocke had a chance to tell her story, it would be great  to start with the genesis and have an understanding 
 I think maybe like  right as shes getting out of university and before her whole familywe  jump in right before all of her family is taken out and we have an  understanding of what she had to lose. Then her figuring out her powers  and how powerful she is. I think that would be a great thing to, because  its something that I always loved about her. That she came from a good  family and lost everything. Yeah, I would just like to tell that  story.