Well, as Preciselove mentioned, there's a lot strung all rambling together.
But from what I could pull out of it one thing came to mind.
It's seems entirely possible that she may just not be either into you sexually (giving to you) or may be uncomfortable with her own bisexuality. She is kind of ok with you taking care of her but mostly because he's in the picture. Alone she might not even go for that.
This is a guess.
However, even given this, it's entirely possible for you three to have a nice relationship. But you (especially her) all need to just be honest about the little details like this. There's ways to express our preferences without it being personally offensive. And ways to HEAR these preferences without taking it personally ! Adults - right ?
It can absolutely work for him to be center of attention and you guys to be close friends with some sexual boundaries. And maybe you can continue pleasing her (if that means a lot to you) without expecting her to reciprocate. You can work that out between you. Just be honest about desires & comfort levels. In short - be respectful & loving !
Good luck !