As I told David in the other post, I think it is important to wait until they come to you for help, so as not to inadvertently force your hair insecurities on a perfectly happy kid.
When I was a child, I had always known that my mother had received electrolysis on her upper lip. I was aware of the electric razor in the bathroom and my grandmother’s use of it. So I guess I always knew of the genetic hair issues I would eventually deal with. Discussing your own hair issues might help open up the topic to your daughters, without them feeling a need to discuss their own.
I’m sure you have a pair of tweezers in the bathroom. When I decided I’d had enough of my unibrow, I simply picked them up. Eyebrows are a relatively small area, so I wouldn’t be concerned over more drastic removal unless your daughter wants it.
As for upper lip hair, when I told my mom I didn’t like it, she waxed the area for me. I’m not sure why we chose waxing, but probably because my older sister was already using that method. I found that waxing worked fine for me. I actually bonded a bit with my sister and mother during those times, and it lasted longer than shaving but without the embarrassment of going to a professional. Now that I’m older I simply wax myself. It takes me no longer than five minutes and I can do it whenever I need to, without having to make an appt. Furthermore, I feel no pain in that area.
I hope I haven’t rambled, but my point was that it should be your daughter’s decision, and all you need to do is provide her with the information and support she needs. As she gets older she will have to make more and more decisions about her body, so it is important to let her know that it is her body and her choice – no one else’s.