Wow thats pretty heavy Kiya you poor thing. What DNA was done the first time round???
I too had a DNA test done on my son as his father didnt believe me and it was just a mouth one that you can do at home and it cost $500 and it came back 99.99999999% that he was the father. I could not use it for legal reason or to claim child support as there was no 3rd party to witness it, that one was $1000. Cant your DH just sign away his parental right for her because he doesnt want anything to do with her???
Im pretty sure that would send a message loud and clear and would cut her up. My friends ex signed away all his rights to his son and she was very very angry and upset.
Get yourself a new email account so you dont have to get anymore emails from her.
Stand your ground and dont let her get in the way of your plans or your family. If you let her get to you then she wins. I think even if you get a laywer to send her a letter telling her your DH feeling and to stay away or court action will be taken then she may back right off.