Several of the senior women instructors at Keystone this season were on t-nines. I was surprised they went for "womens skis" but they were very pleased with them.
I loathe womens skis, but like someone else said, they are made for lightweight people (some womens skis are good for light men).
The better brands also do things like make the mountpoint a fraction forward, change the flex pattern and maybe incorporate a slight ramp.
Women often have their backsides a bit lower/legs shorter in proportion to body than men, and their weight is slightly further back. Some have a shorter achilles. So skis that recognise this can be great for some women.
My favourite K2 was the Mod X pro, I demoed them in a 187 which was way too long for me (i'm 5'3"), but i loved the rubbery rebound. If I ever see a pair going cheap, I'll grab them for sure.