It sounds like your girlfriend has a lot of issues possibly (some mental some substance abuse) Of course, it is possible for a person to act out and make poor choices without this being the case/cause.
Of what you are describing - her erratic behaviors, change in mood (staying in bed) and drug use could be indicative of untreated or undiagnosed mood disorder such as bipolar disorder. Also, possibly unresolved trauma from the abuse you've mentioned.
This is a lot to handle on your part (whether or not she has a disorder); just the behavior itself is something disappointing and undesirable.
If you have been together for quite some time, you know her better and how she acts and what her mood is like. It seems that she herself is either unsure of what she wants and what is going on with her emotionally or that she knows and is trying to get the best of both worlds (that of being in a committed relationships and that of being free to chose and do as she wants like a single woman would)
You could see if she would be willing to in for some therapy and a medication evaluation if needed. Without proper diagnosis and treatment, it is unlikely that she would get to fix these on her own.