What should I do? Please help!?

Okay, so this is like advice needed. Im gunna use fake names for the protection of others. I like this guy (we will call him Bob) and he is dating this girl (chyenne) and they have only been dating for like a couple of weeks. they dated at the beginning of the year and like that lasted a couple of days. I used to be friends with chyenne but that was two years ago. we werent really good friends, we just talked in homeroom. my friend (melanie) is friends with chyenne and she really hates Bob. but the thing is chyenne doesnt know that she hates bob and stuff but i know that melanie hates bob. bob is a huge flirt and flirts with me and we used to like each other a couple months ago. i stil like him but like melanie says that if i continue to like him she wont be friends with me because i know that she doesnt like him. but like shes friend with chyenne still cuz like chyenne doesnt really know that melanie hates bob and stuff. and like melanie like is trying to help me and i know it but idk what i should do... any advice?!