I had a friend who has schizophrenia. I want to mention it, because the symptoms do look very similar to a bipolar disorder - even the physical roots of both illnesses can be the same (a lack/abundance of certain neurotransmitters).
If the cause is bodychemical, then there are afaik no non-prescription drugs there, that could bring the back the balance, which you can legally get. However to determine the disorder you need the help of an professional, I can't preach this enough with the choir here. I had to give up my own aversions against quacks when fighting with and for my friend. No matter how deep your relationship is, there is a point when you reach your own limits and it looks you are at this point atm.
A good first step is realization: that she realizes that she has a problem. A step further would be acceptance. I am mainly talking about her, because without her realization/acceptance and the will to change anything you'll be running against walls. I can relate to a hatred against injections or pills, have it myself. But the one thing you can try to get into her mind is that she has a malfunction in her body and just like a person with diabetis or high blood pressure can have a normal life with these little chemical crutches, she can have this too. Though it's very advisable to have an accompaning therapy.
It looks like have come to a crossroad in your relationship, the question you have to ask yourself and your heart is: are you willing to go through all this with her together? You have to answert this for yourself, but what I've read from you here is that you strike me as a fighting type who is not willing to go down easily.
With my friend, I went through a lot, invested a lot of time, sweat and nerves. We even managed to get him out of a mental institution to take care for him - my girlfriend is a social worker, so she could put in some weight there. Unfortunately, this all went to shambles, though we didn't give up after some backlashes, there was one time to put an end to the friendship, after some betrayal. Another reason is that he was not willing enoguh to realize his state and work on it, for example he did too many drugs which were quite contraproductive to the pills he took against his illness.
The morale of this little story: fight for her if you feel something for her, if you give up, no one has the right to judge you and throw the first stone.
Good luck and my best wishes!
