OP - It is interesting that with a rising 9th grader your focus was on time and pickup elements of life. I also think it is important to start helping her to say "No" to other things that even girls might be doing, especially when at an overnight sleepover such as being offered alcohol, pot, or other pills.
At some point there will kids experimenting and even the best kid might make a mistake and want to share.

I can remember when we purposefully decided to be the drivers for a 'nice group" of girls between where they were having dinner and the home coming dance. Little did we realize that someone had a bottle of something some shared between dinner and waiting for us. They advised DD not to try it as they knew she did not drink, but they basically had an open container in the back seat of our wagon!! So you see no matter what you think you might have rules and plans for, life always offers surprises.

1. Well before dark, texting me before she leaves, or I'm happy to pick up.
2. I'm willing to pick up as late as 10 or 10:30. To be honest, 9:30 seems to early to me.
3. Just offer to pick up if it becomes a common thing
4. Like others said - HARD NO. This isn't ok, and I would let the parents know it is happening. If I was told you are at friend's house, that's where you are unless you ask and are given permission to be elsewhere (like a quick text "hey mom, we are going downtown for ice cream, back to friend's house by 9" "ok hon, text me when you return to Betty's place and have fun").

^my kids don’t have curfews but I expect to be informed of a general plan. And if I say they need to be home at 6:30 on a given day because we have evening plans then it needs to happen. It is about mutual respect. I don’t need to know every detail and they know I won’t be mad if they call or text that they are going to be late.