Hi there! Not sure I'll be of any help, but when I was going through menopause 2 years ago (I'm 53 now), I definitely had dizzy spells and some light-headedness, which I was told can happen during menopause due to the lack of estrogen being produced. I would think that having one less ovary would mean you have less estrogen being produced? But I certainly don't know this so don't go on just what I say! I have no idea if the remaining ovary produces more estrogen to make up for the missing one? Doesn't seem like it would, so my guess is that your daughter's body is adjusting to having less estrogen produced (kinda like a "mini" menopause). Thee's a great website called "34 Menopause Symptoms"
https://www.34-menopause-symptoms.com. I found this website very valuable while I was going through menopause. Like I said, this might not be what's happening with your daughter; I'd suggest she go see her doctor just to make sure!
I agree that it may be the loss of her ovary and its hormones that triggered this especially since it also happened to the EMT's daughter. Hopefully, her body is still adjusting to the hormone changes and this will be an isolated incident. A visit to her primary care doctor may be a good idea to rule out other causes.
One other thing - My blood pressure has always been on the low side but it went even lower after my ovaries were (unnecessarily) removed... sometimes in the low 80's/50's. I had episodes of lightheadedness and shakiness but no fainting. A woman posted a similar experience on the Menopause forum.