My reasoning is that if you're already placed on a "Nice. Caring, Kind" pedestal, you're only going to reinforce those same traits if you continue to live with/support her as she grows up.
She would always look up to you, always compare others to you and probably find it hard to accept anyone else because she's already got your unrealistic ideal planted inside her head.
Continuing to be friends with her after the reject would give her both unrealistic expectations from others and something to constantly strive for what she ultimately can't have.
You'd be an anchor in her life. Weighing her down in a constant attempt to appeal to you somehow. It's intruding, even if all you're doing is being friends with her.
That's just my reasoning though. Feel free to tell me how I'm wrong. Any way for this to work out is a good one.