I been dating my gf for 2 years and everythings been fine. Then all of a sudden one week she had alot of stress in her life and began acting extremely strange and erratic. Her behavious started to become irrational within a few days. It’s been a few weeks since she started acting this way and she accuses me of spying on her, things everyone is a spying on her including government, her messages on social apps are hard to comprehend, and are extremely irrational. 

What sort of mental illness is this and will she eventually get back to how she used to be like for 2 years?

Note: she is in psychiatric care atm but doctors wont tell me anything