I honestly do not miss her at all anymore. I do miss what we had in terms of a family. Never in my life (i am 33) did I ever think that I would want children. I never thought it was possible to have such a bond with someone. I hate her for taking all of that away. I see her son and I know he must be confused. He lived with me for more then half of his life. I know that he want's to be back here, and have things the way that they were.
I honestly believe it should be illegal for anyone with BPD to get involved in relationships with anyone.
I'm sorry this is difficult. You have a lot of and a bond with the child. Kids change your life and I understand. I came across something a year ago on the internet in regards to men and divorce. It may help you, it may not.
Some men feel like the shackles have been broken and they are set free when they are going through separation and divorce. Some men it is devastating and they become depressed from losing their place as a husband and a father, having a place and routine in a family. I placed in the second category, the fallout of the r/s was much more painful because I had lost "my place" in a family but I had to let go of my ego. My wife and I are two different constellations now, I have my place with my kids and she has her own constellation. I'm a single father (a young family) with 3 children.
I'm Canadian, so the laws are different here but perhaps you can call a lawyer and get a 30 minute consultation and see what rights that you have as step parent and if you have visitation rights. Another possibility is if you have a good r/s with the father, perhaps you could arrange something through him? What is the little ones father like, if she lost custody there has to be something good about him because she lost custody due to drugs? You don't miss her, maybe you can arrange visitation through a different venue.