I can see where my question left enough open to be confusing. We live outside our school district and DD does not hang out in the neighborhood or suchlike; it's just that she and I do best with *very* clear guidelines. For example, if I drive her to a friend's house without a clear "curfew" time to get home, depending on the friend's parents, she will try to get away with coming home very late. If I let her get away with coming home from Susie's at 11:00 but then tell her she has to come home from Katie's at 9:00, I'll have hours of whining and arguing ahead of me.
It hasn't helped that DD's best friend's mom is way too permissive - she dumps her children at the mall or local ski area and leaves them for 10-12 hours. Her daughter has a habit of getting a ride somewhere without planning how she's going to get home. A few weeks ago, she and DD went to the movies with a few other kids - one parent was taking them and another was bringing them home. I got a call at 8:30 saying that the "taking home" parent hadn't confirmed and now the girls had no ride. I got to the theater at 9:00 to discover that the movie didn't end until 9:40. At that point, three boys also said they had no ride, so I took them home as well (luckily, I have a minivan). What a mess.
Anyway, with the (ahem) relaxed parenting among DD's friends, I want to be very clear about when she needs to be home. I already have a contract of sorts drawn up that requires a minimum of 24 hours advance request as well as parent phone numbers so that *I* can call and confirm all the details before I'll even consider the request. And for the sake of consistency, I was planning to give a base curfew of 9:00 for random visits and such. I'm anticipating howls of misery over how unreasonable that time is, but her safety and my peace of mind are much more important than her embarrassment over her mother's strictness.
Thanks everyone for the input!