Let me see, two unaccompanied 10 year old kids, after dark, at a party. It doesn't seem at all like riding Tower of Terror to me. And it doesn't seem like a good idea to me, either.
I understand it's not for everyone or every 10 yo, but my DD has been to WDW 15+ times, knows the parks very well, and is very responsible. She won't drink off of anyone else's table, annoy other guests (apart from some likely giggling) or become scared/confused.
Riding ToT unaccompanied seems like it could potentially be the more challenging scenario, as the ride could break down and she could be stuck. But she's been riding by herself (and exploring the parks to a limited degree) since she was 8, so I am very confident in her.
As to other guests, if someone is misbehaving, I'm not sure what I could do to protect her better than she could herself. She and her friend would be very capable of alerting a nearby CM if anyone was causing them issues. She's seen plenty drunk people at F&W and has lived to tell the tale. If anything, she is normally amused by their antics.
ETA: She has a cell phone and charging privileges on her MB. If she runs into any issues, she knows she can reach me. If she needs money for anything, she is set. To me, personally, it's a very low-risk scenario with a high reward. I completely understand if others don't feel the same way. But I am really just concerned with whether this is actually allowed/feasible in Disney's eyes.