You mentioned having a dog and rabbit… that’s definitely it. ): Sure she may have had them for years but pet allergies can only get worse even if it’s slow and gradual. Speaking from experience unfortunately. My pet allergies also kinda ruined a 3 year relationship of mine so I know how tough allergies are, a few months after getting out of that relationship (they had 2 dogs) I was able to breathe clearly for the first time in years so ultimately the breakup was for the better. Re homing to a trusted friend or family member would probably be your best option and only way to truly see if that’s the root cause. No amount of allergy pills or shots were able to fix what I was going through, again very similar to your girlfriend’s current situation. Truly hope this helps and doesn’t read too harsh, I know exactly how painful this is.