Are you diagnosed with npd, or have you and your girlfriend home diagnosed?
I ask because I have 2 sons both on the spectrum....both very different but my older son responds similarly to what your describing.
I find it is common for people to mistake and confuse these behaviour types.
I would advise working with a professional to unpack the two behaviours to ensure proper management of both.

I wish you and your gf all the best for your future together.