That has to be up to you but you need to read up on NPD and find out whether you want to spend the rest of your life dealing with this. If you are not fully committed to setting boundaries and being strong and secure in yourself then you will find it too difficult. But it isn't wrong to want to try and make a relationship with someone with NPD work. Just remember you can walk away any time you need to, anyone else would, and you need time and space for yourself. Good luck!
It depends on how long you two have been together. Surely she needs your help at this time. And being dumped is not going to help her deal with her problem.