Her and River Song are most definitely related to each other in some way. River knows too much, Amy is at the centre of all the shit that's goin' down. Check out the first Angels epsiode again, they're both wearing the same gold watch.

I know that's hardly definitive proof but it's not the sort of thing they'd do by accident, in the same way as the future BizarroDoctor coming back to chat to Amy with his suit jacket back on in the second Angels episode.

It's all very...amazing