Hi and Welcome,
I`m glad you found us.
We can offer support for you as you try to get yourself clean. I don`t have experience with heroin but others will be along who may offer more advice.
It`s not a good idea to plan to get clean with your girlfriend. Honestly, recovery is a very personal journey and I think you will need to focus on yourself and your healing. Your girlfriend will need to seek support for herself if she wants to stop using drugs. You can`t do that for her.