Just because he doesn't want to shag her doesn't mean he's not jealous that someone else is taking up her time. Unless there's something you're not telling us, it sounds like he's annoyed that his bestie is giving time and attention to someone who's not him. Has he ever approved of any of her relationships?
Lots of law students handle this kind of think pro bono. Also not great lawyers work with quite small contingency fees.
Just because he doesn't want to shag her doesn't mean he's not jealous that someone else is taking up her time. Unless there's something you're not telling us, it sounds like he's annoyed that his bestie is giving time and attention to someone who's not him. Has he ever approved of any of her relationships?