if i'm a legacy does that mean i have a good chanc

Legacy status has nothing to do with what school she went to. If she was an ABC, you're a legacy to ABC no matter what school you attend.

With that being said, legacies usually get paid a little extra attention to, but it by no means will guarantee you a bid. If anything it'll just get you an invite back to the next round. This is a good thing, because it means that if you DO get a bid, it won't just be because you're a legacy, it will actually mean they like you. You don't want to get into a house just because you're a legacy. And houses won't give out bids for that reason alone either.

And yes, she needs to either write a rec or send in a legacy form depending on what her sorority requires.