It sounds like your hospitalization was primarily for your safety. As for processing what happened to your girlfriend, it might be very helpful to find a therapist. Medications can be helpful, but I think without therapy, progress is much much harder. I would see therapy as the first-line treatment for PTSD, with medications a support.

I never really found much therapeutic support inpatient, either. Even IOPs weren't always that helpful. It wasn't until I found a good private therapist that I made progress with issues outside of my bipolar disorder.

I hope that you can find helpful support soon. I hope your girlfriend has good support, as well.