This is subjective, but for what it's worth...
I've skied the Pandora, the S7W, the Kiku, the K2 MissBaker and Gotback, the Atomic Century. Bought the Century. (I'm more or less the OP's size)
I liked the Pandora a lot. It is extremely maneuverable and fun and forgiving, did well in tracked out and bumps and windblown coral reef as well as powder, but was not happy in that delightful in between refrozen and soft spring condition. If the OP is going to use it only to help her deal with powder, she will likely be happy with it. It is not a one-quiver ski IMHO.
I personally do not like the s7W at all, found them not that floaty, very unpredictable and simply a PITA in crud...so endorse the advice to demo since I'm clearly in the minority here.
The Kiku is a fantastic ski, but it demands attention and if she's having trouble already, it might not be good choice. Despite rocker and no camber underfoot, i didn't find it at all a problem on groomers back to the lift, even hard pack groomers. It is a fun and very steady all-terrain ski.
The K2's was OK but, maybe because it is primarily an AT ski, the Miss Baker felt flimsy, and the Gotback skied too short, so my fault for not going longer with it.
Atomic Century was my eventual choice; it is a very forgiving and versatile powder ski, so one she might put on the demo list.
Second Trekchick's admonition to go longer, much longer, in a rockered powder ski.