Morgause and Hera probably would not have gone to school together; I don't think that the Cosimos would've been able to afford a private school kind of gig. Buuuut family friends, maybe? Through their mothers? Joana and I have that CR set up for Medb and Hera, so it could work?
Theseus and Minos are welcome to have met her at some point! They're around her age. As a teenager, she was very "I'm gorgeous", very flirtatious, very "come adore me" but also extremely untouchable. Zeus got to her when she turned 18, so by that point she was a faithful wife-y wife-y. It depends at which point of her life you want them to have met her! :D
Bodaaa, bb girl ♥ And Lilith *o*
Also, she could have played doctor to Theseus, Minos or Lilith if something ever happened to them while they were in the UK.