I am neither a doctor nor an expert in insurance, but this is a simple question of resources. If your girlfriend has special needs that are paid for while she is unmarried, rather than usurping the rules of the state, you need to do some due diligence before getting married. As the state (apparently) is not engaging in any unmoral decree that keeps you from marrying, you need to see what options you will have after marriage. Granted, her current means of funding may change, but if her condition is as dire as it sounds, I tend to think she has other avenues to go down.
It’s a tough decision, but I hope this helps!
In His service and in yours,
Christ Lutheran Church & School
Coos Bay, OR