Hi A.,
I wanted to chime in on the advice for your daughter. First of all, you sound like SUCH an in-tune, sensitive, caring mom, and I'm telling you, that, above all, is going to help her weather this problem. :)
I'm speaking from experience - as a child, i was a chronic bedwetter. I actually wet until i was a teenager (don't tell your daughter that, though, for fear of discouraging her)... and your post hit home for me. Sleepovers were a big issue for me - i wanted to be involved so much but would often find excuses not to stay the night. My mom would tell my friend's mothers (sometimes), in an effort to just minimize any "damage" but still allow me to go. Sometimes that worked, but i would be nervous the entire time.
Anyway, mine was medical but nothing specific.... i had a small bladder and many urinary tract infections. that was about the best they could do in terms of explaining it. i DID grow out of it - just took a while.(and i was an extreme, i think)
We had an alarm for a short time, and I have to say i don't recommend it - not only did it not help but i ended up, in my sleep, turning it off, b/c the jolt awake was so horrible. Also, we had a buzzing one and it was only recently that i could play a popular board game that used a buzzer - it used to drive me crazy before, just b/c it was such an unsettling (and familiar) noise.
A few thigns that DID work - I remember getting something called DDAVP nasal spray. You may want to ask your dr about it. I dont' think it is specifically FOR bedwetting but it hadd been shown to work. This is years ago, so i don't know if they still use it. But i remember we had the most success with that.
Another thing i remember doing/checking - is your daughter's bowel cycles. The theory there was that if your daughter is constipated, it will put pressure on her bladder, not allowing it to expand as it needs to at night. I remember keeping a calendar of days i "went" and days i wet and alot of times you'd see some patterns. It's worth a shot.
It's definitely hard - i was sensitive, too, and it was an emotional thing b/c you can't control it and you do feel differently than everyone else. But the best thing you can do is what you're doing - being sensitive to her issue and being supportive and loving. There is nothing worse than adding shame to the embarassment she probably already feels. She's lucky to have a mom who is putting her emotional needs first. :)