twins being legacies?

Someone correct me if I'm wrong, but I don't think she'll be a legacy. In order for her to be a legacy you would have to be an initiated member, and unless her recruitment is after your initiation then you'll only be a new member when she goes through. But the sororities might see that you just pledged whatever sorority you pledge just via social media or her conversations with actives, but she won't be considered a legacy unless you're an initiated member before she goes through recruitment.

I'm not 100% sure, but I don't think she will be if you aren't and initiated member yet. I had a friend whose twin sister went through recruitment in the winter (that's just when her school did it), but her twin that went to Alabama had already been initiated for months so the twin that went to the other school was considered a legacy. However, you are not a full member until you are initiated so I don't think your sister would be considered a legacy unless her recruitment was after your initiation. I would definitely ask your recruitment chair of your sorority once you join just to double check and things are different for every sorority so you never know. it'll also be easier to secure your sister recs or letters of support (if she needs them) for recruitment even if you're a new member. Your sister could always "casually" tell actives at the chapter at her school that her twin sister had just pledged at Alabama and that would probably make a difference, too.

They are right. You must be an initiated member. Now if she doesn't rush until the spring and you were initiated in October, yes, she will be considered a legacy.