How can i help my girlfriend with being bipolar?

i been with my girlfriend for almost 2 years shes 18 and lately shees beeing cryin all the time n depressed it kills me i love her more then anything in the world and i want to help her she went to the doctor a few days ago and they told her she was bipolar nd that made her worse and they wanna put her on meds i feel like lately theres nothin i can do to make her happy i wanna help her with this but i dnt know what 2 do i know s*** about this stuff she gets paranoid all tha time now she thinks because im older then her that ima leave her i tell her im not then shes fine for a few mins then she has huge fits i dont know wat 2 do i love her alot id neva leave her i wanna help her be happy again what can i do 2 help her