if a fan of twilight told me that I have a bad taste in movies?

Clearly her saying that is just her opinion. I myself am not a Twilight fan (more of a Buffy fan), but the fact that you felt the need to specify that your friend is in your question is funny. I understand if you said it to add credibility and background information to an answerer’s answer, but that would create a more biased answer. If, as I believe you did, post this for a certain reaction or to justify that it is okay to tell your friend off because she likes Twilight, then tell your friend what you want, but do not try and justify an answer backed up with biased evidence and more opinions.
Not meant to offend you, but rather inform you that you will not get (most likely) responses that are consistent and agree with the social mores of our time.
PS I myself would tell my friend that I could say the same but choose not to. I would not justify it though, because it could be rude and hypocritical.