I think she has enough information to not call it perseverance:
- She knows that he has been rejected multiple times and she has already rejected him on behalf of He Fang;
- She knows that He Fang wants nothing to do with him;
- She knows that He Fang has a boyfriend;
- She knows He Fang finds it annoying.
She's rejected him for her, where he would have acted like he did initially; calm, polite, reasonable. Not freaking out and self-centred, because he saw her with another man and couldn't handle it and let his true thoughts come to the surface.
Saying that "he has nothing to do with me" doesn't inform against perseverance at all, but in fact the exact opposite.
He Fang is saying that the entire situation is annoying, because the others don't know the other side of the guy, and now she has to get up and deal with him. If anything, that attitude would increase someone's curiosity, not assuage it, as to why she holds that attitude, having a suddenly-appearing boyfriend that they've never heard of from her or not; in fact, considering the suddenness, it probably looks more like it's a fling, not something substantial.
Note again that He Fang didn't get upset with the girl for asking, and answered matter-of-factly, and the girl also didn't reject what He Fang said in explanation.