I don't understand why she's madly in love with him...

my cousin loves this guy. i know because i can see it in her but i don't think this guy is suitable for her. i don't think he will make her a better person. sometimes i feel that i am such a hypocrite. i smile at him whenever he sees me but deep inside i feel sorry for my cousin because she's madly in love with him. i know that i shouldn't be interfering with their love lives but i just feel so concerned for my cousin. she's always scolded for going home late what's worse is she went home late because she came by her boyfriend's house. i know that he cares for her but what i don't understand is his concern for her is not consistent. he gets jealous easily but when she catches him somehow flirting with someone else, he doesn't see my cousin screaming about it. i don't think he loves her because he finds it easy to break up with her. he always says that to my cousin whenever they have a problem. it seems like he is so ready to leave her. it's as if he already has someone new.

But what can i do? i'm just a person outside their relationship.