If you unknowingly infected your partner with an STD, how should you handle the situation?

I think you are doing fine, give her the space she needs, but still be there for her. Distant might be her being confused. Reure her that you are getting treated, and will have regular health checks to make sure you are healthy. And yes, if you are faithful to her and don't cheat on her you won't need to do that, but given her bad history with guys it's can't hurt.