I was thinking of avoiding it for a while too, seeing as Avatar is still very busy and that's been open for like 4 years now. When I heard people were actually waiting 8 hours a few months ago to ride the new Potter ride I thought it was ridiculous.
Luckily, with the hurricane coming, it was actually bearable being there! Its kind of sad when you hear "110 minutes" and think that's not bad.
The lines were apparently even better today from what I heard.
I just walked around yesterday though but I plan to go back later this month for my birthday. I went last year late September in the middle of the week and it was amazingly empty- by Disney standards (only waited 30 minutes for Avatar). So your sister might luck out!