Wow, someone with the ballz to join the MILITARY to get clean, and then balks at REHAB?
This lady must have SOME inner strength to go to those lengths, only to blow it. My guess is she feels guilty and bad about falling down so hard after that incredible effort. Likely she is also using those bad feelings about herself to continue to abuse drugs, using the logic that "I am bad anyway, so I might as well use."
Take care in getting involved with an addict. This may be a relationship you can't sustain, and if you are a young guy, you have your whole life ahead of you to live with a clean and sober person who may end up being the mother of your children. Be careful. Don't linger longer than is wise.