Mother with PTSD, depression, and anxiety

Need some advice on how to best support a parent with mental illness. I am 23 years old, my mom is 43. I recently graduated college and she recently retired from the Air Force. She has been struggling and nothing I do helps.

I moved back home after graduating but I want to move out soon but Im afraid she won't survive if I leave. When I leave home even just for a few days she sinks so low and basically becomes paralyzed. She sleeps all day and doesn't leave the house.

Has anyone ever experienced this and what did you do?