“If the only way I can become her friend is by telling her that I might do things she does which are against halacha, should I? Is that not hypocritical?”
Ask your LOR. Many Poskim say that when doing kiruv you are not to compromise on your morals and beliefs or say things that are not true. Lying to her about your opinion of movies is probably not the best idea.
In regards to music and movies, you can say that the same way there are ratings on movies to indicate what they deem as the appropriate age for a particular movie, so too in Yiddishkeit there are certain things that are deemed inappropriate for certain age groups and at certain points in life (premarital)