I Don’t Like My Man’s Female “Friend” [THE SCENARIO]

One of my listeners is having a difficult time with the company her boyfriend keeps...she wrote...

When my boyfriend and I met he had a "best friend" that's a female. I was cool with it at first but I feel like she likes him a little more than he might think. I tried to bring it up to him before and he thinks I'm just being jealous. The way she looks at him, the things she tells him and what she wears around him are all suspect...do you think I'm just tripping? Do you think it's ok for a man to keep female friends if he has a girlfriend?

Thank you!