Is this weird or what for a woman?

This guy I know has a jealous gf that won't let us hang out as friends and know hates me because she got mad that I texted to hang all the time. Anyways she didn't trust him and called him a lier. So I guess he felt obligated to prove himself to her. They're suddenly engaged after breaking up a few times, but he pops her a ring and suddenly she believes in him? Is this weird or what?