Jake,
This isn't easy for you is it? My youngest is 22 as well and I know how hard it is for him to listen to my advise.
It is hard for you but I think you hit on the right way to go. Let her stay on her father's insurance. If as a graduate, you start your career, and you earn enough or you get insurance from your employer, you can always change things then, before she graduates.
I am not talking down to you when I say if it is love, real love then you can wait 4 short years.
I hope this helps.