What to do, besides call 911, if friend has grand mal seizure? It was her first one. She has hemiplegic migraines. Was so scary I just froze...

Go to local ER. If possible, take your friend to emergency dept, as convulsions can be due to a variety of events, and there is always risk of additional spells if not treated. Although the migraines may relate, the first order of business is safety. Your friend should not drive, do activities at heights, operate power equipt. Until things are stabilized. A neurologist should be involved.
Neurological. No individual advice can be given, but if someone has a grand mal seizure for the first time, it requires immediate neurological attention. Supporting follow up for neurological assessment and any recommended treatment is the bes thing one can do.