The girl I'm with is having a hard time getting excited cause of her ex!?

So im dating this girl when i started seeing her she was still with her ex. So in the beginning she had no problem getting excited but since she broke it off with her ex to be with me. She cant get excited, she says that the memories get to her. He was her first love first guy she was with and i'm trying to help her get over that guy so she can move on. She's always been a sexual person but since she broke it off with him its hard for her to get in the mood. It's to the point where not even i can get excited sometimes and cant climax. what do you guys recommend she says she needs time and i say we just keep on trying until she gets used to me. This is the first time something like this has happened to me and im a little lost. and like i said it was fine at first the problems started when she broke off with the other guy?