In my household the bedtime routine starts at 8:00 when snacks and any evening bathing occurs. 8:30 - 9:00 is allocated book time, and lights out at 9:00. There are no TVs, computers or cellphones allowed in their rooms. This allows for 8-9 hours of sleep, depending on when they fall asleep.
I know some people need less sleep than others, but at a young age of 11 and rising at 6 in the morning is a long day for a child that does not get the required amount of sleep. I would say no later than 8:30. If the child goes to bed later and does well in school etc, then she might extent the time. It is an individual thing tho.
Depends on how she is to wake. I let my kids sleep according to sleep cycles. A complete sleep cycle is an hour and a half. So any multiple of that ie 1 1/2 3. 4 1/2, 6, 7 1/2...etc. They will wake up at the END of a sleep cycle instead of in the middle of one. Waking in the middle of one will leave you feeling more tired as if you got NO sleep. good luck