Unfortunately, people do change - sometimes for silly reasons like a new boyfriend. I've experienced the same thing, and if you don't feel as though she has your best interests in mind and is looking out for you then distancing yourself might be a good idea. Maintaining peace is essential, imo.

Doesn't necessarily mean you have to stop talking entirely, but you have to preserve your own energy (probably better spent on expanding your social time) and look out for yourself, too.