I personally think platonic friendships between heterosexual males and females aren't viable in the long run. That is simply my opinion based on personal experience over many years. For me, the guy has always ended up wanting to be "more" than friends and I did not want more than the strictly platonic friendship.

A prior T of mine once told me that men and women generally cannot be platonic friends. He said that women seek out relationships others as an extension of themselves and men seek out others with a defined "goal" in mind.

Again, just my opinion and experience as well as my (male) T's opinion.

Saying derogatory things about you to others is not a good thing, obviously. I think that she needs to be communicating directly with you about concerns ... and vice-versa.

Perhaps she is having an emotional relationship rather than a physical one. There is not room for either in your relationship with her.

I think it is best not to speculate and you need to communicate more openly - and get the trust back, if trust has been broken. Honesty, communication, and trust.

Best of luck to you and I hope it works out in a way that is best for you.