Your friend is obviously feeling insecure, and in need of some attention.
This is just attention-seeking behaviour - the need to are-affirm her attraction, especially if her relationship is not going well.
She is obviously jealous, and is keen to make sure that you know what she is doing - probably to provoke a reaction.
How you handle it depends on how you feel about her, and about him.
If you trust your boyfriend, it doesn't matter what she does - nothing is going to happen unless he wsants it to.
But if you feel insulted, and her bahviour makes you feel insecure, you should consider that she isn't being that much of a friend.
Solution - you can either ditch her, or, if you feel your friendship is important, have a chat with her about her boyfriend, since her relationship with him is at the root of her unhappiness, and her subsequent behaviour.
Have a think about it - maybe she is trying to get some attention from you as well, but just doesn;t know the right way to go about it.
I'd be inclined to try for a chat - if it blows into a row, then at least you have tried.