Well...I'm not a mental health professional. So I can't respond to this in any authoritative sense. But my personal non-professional perspective would be that the only person who can help your girlfriend is your girlfriend. If she won't do what she needs to do in order to figure out what's going on, & what she can do about it, there's nothing you can do to change that. And as far as keeping "all that makes her spectacular", while doing something about your gf seeing & hearing things, I suspect anyone who can figure that one out is destined to become a very wealthy person. Every one of us who struggles with mental health issues would love to be able to go in & "surgically" change just those parts of ourselves that are troublesome while keeping all of whatever good qualities we have. Unfortunately, at least at this point in time in the history of mental health services, that rarely happens.

Here are links to 2 articles, from Psych Central's archives, that discuss how to convince a loved one to seek professional care & how to help a loved one who is in denial:

How to Persuade Your Loved One to Seek Professional Help

11 Ways to Help a Loved One in Denial

My best wishes to you both...