Should I tell my best friend that I don't like her boyfriend?

I have this best friend we have been bff since I can remember but she is dating this guy who I don't think is right for her and he like tried to get with another friend of mind so she told my bff and then they supposedly broke up then I asked her the next day does she still like him and she said yea we never broke so should I tell her what I think or stay out of it?

yes a friends advice is always right and tell her whats going' on if she doesn't listen find evidince for it

Sure, speak your mind and let her know you don't feel he's right for you. But you don't have to do it in a coming to Jesus way and make the topic be the end all be all of your relationship. You can casually mention it if it comes up, but don't beat it into her or continuously talk smack about the guy. And don't expect her to dump him on your advice. She won't do that until she sees the light herself.

Be polite, speak your mind if asked, leave it at that.