Inform her parents about he date , along with the place, and time she will be back. Safety comes first. Better safe than sorry. It may not be the coolest thing to do. But god forbid anything goes wrong
Acceleration is basically how much faster you're actually getting each second. Velocity is the speed of something going in a particular direction, not how fast it is getting.
The pairs of activities that can best help a dancer develop better stage performance would most likely be muscle-strengthening and balance/stretching.
When you think about it - dancers obviously need muscles to a certain extent in order to be able to move in a specific way but they also need good balance and the ability to stretch. All of these things play an important role in dancing :)