Not sure about medications for treating balance, but is her balance issues from dizziness, weakness or just feels off balance? If it's dizziness, she might find some relief from motion sickness pills, they help me when my brain decides to flip flop around.

If it's due to muscle weakness, core exercises and some strengthening exercises would likely help, I would strongly suggest going through a few PT appts to ensure she's targeting the proper muscles to focus on posture and center of balance.

If however her balance issues stem from kind of a disconnect in the nerves that simply doesn't allow her to "feel" balanced, one trick I found is standing on one leg while bouncing and catching a tennis ball with the opposite hand. You can start off propped against something, but it seems to 'trick' the body back to its natural balance. There's various other balance related activities that can be done. An OT or PT should be able to help her out, but even just a quick net search will give her some ideas. Of course if she has the money for it, the Wii fit is tons of fun and has many balance related games.

Best of luck, hope she finds a way of coping with it.