Buy her a spa day or coupon with a massage or something nice that she likes and include the hair removal option as extra.

Once done make sure you let her know how much you liked the shaved areas. Hopefully she will catch on and continue doing it herself. Otherwise repeat the process. There are even some places where you can buy monthly subscriptions she can go to.

Avoid confronting her on this. Not worth it and you could hurt her feelings. Of course it depends on your relationship with her. If both of you feel comfortable talking and discussing such topics then go ahead.