I'm glad that you two sisters can have so much fun talking about working out!
My sister is a former aerobics instructor. She's trying to get back into it. She's tall and lean but still has a B-cup and a a bubble butt (Oh, the roll of the genetic dice. Sigh!) - 5'10", size 6. Maybe 130-135 lbs? She wants to teach BodyPump so I'm hoping that will help her slide toward heavying up. I hope that I can get buff enough to encourage her to step into the free weights room! I think she'd really enjoy it!