I would recommend helping her by fixing the bike up and extending her the offer to help her get comfortable on it. After you do that, I'd let it go and wait for her to make the next move. I've never taught an adult to ride a bike before, but I imagine that it's harder than teaching a child because adults usually have more hangups and they fall harder. I don't mean to sound pessimistic, but unless she demonstrates a strong willingness to tackle the learning curve, she probably will not end up being a cyclist.
That said, kudos for being a cool brother.