As one who is uninsurable and without health insurance, I can certainly see your urgency in trying to get this taken care of while your daughter is still insured. However, also as one who was told at 27 that I would need OHS within 5 years and didn't do it, (still haven't, and I'm 54 now) I can also see your daughter's point of view.
My personal opinion is that it's time for another opinion. The past doctor has essentially fired him/herself by dismissing you with no follow up.
Since this sounds like a difficult situation, what I would do if I were you, is to go to one of the renowned heart hospitals for another opinion and diagnosis, course of treatment, etc. It would be a little expensive to leave your immediate area (travel, hotel, etc) but IMO it would be well worth it. And do this while you still have coverage. As far as your daughter and her fears are concerned, I sure don't blame her, but this doesn't mean that anyone is necessarily going to suggest surgery now - and even if they did, the very good heart hospitals have more minimally invasive treatments, and MUCH more experience and expertise than anywhere else.
What I would not do is wait and do nothing. Her only option after her coverage under your policy runs out would probably be a teaching hospital, and her situation sounds too complex for that to be the best solution.
What I am having to do, since I am symptomatic now (rheumatic heart disease) is to go to the teaching hospital for tests, and take the test results to a cardio at the 'famous heart hospital' for a consultation and diagnositics. They don't require a referral - you can self-refer, and they do not require insurance - in other words, they accept cash, but then there is only so far I can go with them for that reason. I haven't had my first consult with them yet, so I'll have to see what they suggest and what happens from there...(and tell your daughter I'm scared to death to go back to a cardiologist too! - or don't tell her! lol)
I hope you'll get ideas from others here too!
You have my best wishes - keep us posted.