T-Minus 24 Months

We are one week from age 16. We have made great progress over the past year in communication and how we respond to negative behavior. Some of the negative behavior has been typical teenager rebellion and some more related to Borderline Personality Disorder.
It seems that no matter how much progress we make, one moment of her not getting her way can wipe all of that progress away. Granted these issues are nowhere near as frequent as they have been in the past, they still occur. When they do, it is all or nothing. She will make rash decisions and throw her hands up in frustration, as if all is lost.
Our daughter can be in a good place emotionally and behaviorally and then a minor incident happens, which causes that behavior to change drastically. She will immediately become discontent with the status quo. She will decide it is time to dye her hair again, start dressing Gothic, etc. We really don't care about her hair or clothing, as long as it is not provocative. This behavior is cyclical and very predictive.
Our fear is that as we get closer to age 18, her rebellion will increase, as well as her expectation of more freedom. My wife and I know how she thinks and we know that each day she gets closer to age 18, the more determined she will be to throw the rules out the window.