First of all, I would NOT punish her for skipping school as that is just insult to injury.
I would ask my daughter the details of what was happening to see the depth and severity of the bullying.
Then, I would call the school and set up an emergency meeting with the principal, the school psychologist, and the administrator. During the meeting, I would put a tape recorder on the desk to record the meeting. I would have my daughter name her bullies and recite the experiences, her feelings and how it effects her. Then I would tell the authorities there that if they do not take this seriously or devise a plan to stop this nonsense, I am taking this tape to the local nightly news to have it broadcasted that XYZ School does not take bullying seriously.
You screw with my kid, you screw with me.