Craven Sapphire
Good.
Then he needs to move out and leave her alone.
He also needs to work on his insecurities of opposite gender friends because that's not at all attractive to most women.
It's too bad, she sounded like a keeper.
Good luck on ever finding yourself another woman like that, op.
I don't think OP is jealous at all. I think his poor self esteem makes him think he's not worthy of his girlfriend and he's therefore overestimating her friend's importance.
OP even says he doesn't want to stand in the way of her happiness. That contradicts jealousy; it indicates the opposite.
Insecurities in general are usually "not attractive" and in cases like this it will cause a strain on any relationship. It sounds like this relationship nevertheless was beneficial to OP and probably his gf too considering how long she stayed.
Anyways, I don't know wether OP or OP's ex is on the lease, but yeah, it would be best for both of them if whoever isn't on the lease moves out.
I for one think OP can find another women who will fit him better in the future. Given that this relationship didn't work out it would make little sense to get together with another one like her.