Is it okay to wait for your ex?

My cousin's bf broke up with her & she's still crazy in love with him. They talk alot like they're dating. He says that shell always be #1 but he wants to experiment. So while she's still single & waiting he's out txting, flirting, having girls fall in love with him etc. She's jealous & hurt but loves him so much that she wants to wait. Is she crazy for it? I feel that if he loves her & if she's #1 then shouldn't he be focused on her?