Not officially.
You can use Bootcamp if she has it installed.
On the Mac OSX partition, I managed to get it working, but it took quite a while, and I do not remember how exactly.
It was easy to get M&B running, with a port by Paul the Tall (
http://www.paulthetall.com/mount-and-blade-warband-mac.html). I think there might have been an issue with the mouse first time I did it, not sure any more.
I was using this, and the launcher on a friend's PC to install and update cRPG for a while, copying the folder over, and later I got the launcher to work on Mac via Wine and the terminal, but I do not remember how exactly.
Before I got the launcher to work, I would run the /Mount&Blade Warband/Modules/cRPG/WSE/WSELoader.exe file, which launchs WSE (the old one). With the launcher, you can launch WSE 2, but I suffer big performance hits this way, so I play with the old one.