Solo: my ex was a male version of your GF (ex).
He stopped drinking in 2008, but wasn't working any program. I was with him for 5 yrs and it took a few years to see he was also addicted to female attention.
I finally left because I caught him cheating. He also swore on his kids heads he would never lie or cheat and do to me what my ex's did to me, but he did to it to me, but was even worse than the other ex's.
We even went to couples therapy and he told the therapist I needed to stop this mistrust because he wasn't cheating nor would he ever and that my mistrust was making him want to leave me <---- this is called gaslighting. A CRUEL form of mental abuse!
Solo, in cases like this, I've learned, this is deeper than an addiction, this is a deep and serious personality disorder. The addiction is just the mask to their mental disorders.
Whether her abuse/conduct was caused by past abuse is really not your problem and you are not in ANY way obligated to help her with it.
She needs to step up to the plate and find help.
Many people in this world suffered horrible things from their past, and not all of them are liars, cheaters and addicts.
Getting yourself to an Al Anon meeting to learn to focus on you and to learn to detach is your safest route.
There is no happy outcome to your situation unless you both get help.