I think
Amaryllis is usable.
Odd, but usable. It's quite pretty sounding and not too difficult to pronounce. And
Mary could be a very "ordinary" nickname if she wanted one. I do, however, think that
Amaryllis would be better paired with something more common than the middle names you suggested. And less...old feeling, maybe. I'd suggest something like
Amaryllis JanaeAmaryllis MackenzieAmaryllis OliviaI don't know that I'm very good at this...
Hyacinth, on the other hand, too out there for me to endorse! :)