When ever I try to talk about moving, or try to plan things, she'll change the subject as fast as she can, but not before telling me why I'm making a huge mistake.
That's pretty normal parent beheviour, I think (though I usually see it coming more from fathers than mothers) - the whole "Oh no, my precious little darling, all alone in the world to fend for herself!" veiled by "There's totally 438598 good reasons for you not to go." (Doesn't mean it sucks less, obviously.)

But wow, your sister. I admire your restraint not to slap her, I know I would have (at least verbally).

Good luck with the move and all!! *hugs*