One of the other Mane 6 probably had to convienve her to do it.
doesn't sound likely at all
my assumption of family relation is not strong enough unfortunately. officially, they probably just haven't decided what to do with her yet, but I'd say it is hinted at. I'm betting Season Three will finally shed light on that situation though.
also, Scootaloo's major fangeekiness of Rainbow Dash wasn't a thing until Cutie Mark Chronicles.