The guy, as riddle bro said, is a hypocrite. Let's say he asks the girl. Regardless of the answer he gets, he's still going to be suspicious about her because based on what you wrote, he doesn't trust(love) her. And if he doesn't ask her, he's still going to think the same thing all the time - 'How many boys did she sleep with?' No peace for him either way unless he changes his attitude towards her.

Irrelevant but I wonder sometimes, why do many posts seeking advice, especially related to girl/boy issues start with 'My friend so and so.....'? Why stick your nose in others' private issues? If needed, they can ask for help themselves, can't they? This applies to not just you; there are many alike.