D.B.
It's completely normal to skip them especially at this age. It's actually more common than monthly regular periods! The hormones are just starting and nothing has normalized yet. I'd suggest you teach her to keep a record, even with a code of some sort on a calendar (so it's not obvious to her friends or other visitors to the house), but don't have her hovering over it. The frustrating thing about the first few years of periods is you often have to just wait for them to arrive. If she gets symptoms she can start to learn to identify, great. But many teens don't. It's probably time to have her carry a little "sudden onset" packet in her backpack though!
Then share this record with the doctor on her next regular visit. She does not need a gynecologist at this stage - the pediatrician or family practice doctor can handle this.