Sending you lots of hugs and strength to work with this.
in my opinion, taking the pill may not be a good option. If you don't take it at the same time every day it is not effective. Even a few hours off can make a difference.
If she gets the depo shot it will resolve many of those fights over getting her to take the pill. You will be SURE she is protected.
I believe there is a shorter, maybe 1 day or 2 day, version of the depo shot that lets you know if the side effects will be tolerable. I also know many women who tolerated a severe migraine each time they got the shot, but after that they were fine. For them it was well worth it.
Have you figured out which classes she was skipping? Is her boyfriend an adult, or at least old enough to be charged with statutory rape or contributing to the delinquency of a minor?