My girlfriend is Polish so I have just embarked on trying to learn it.
I forgot to mention in my last reply. You should consider joining the local Polish club. I'm not Polish but used to go with a friend years ago. It would be good for both you and your girlfriend to go.
Then she'll have people to speak Polish with, and you can gradually get used to hearing it.
They have events and traditional Polish festivals. You might also meet new friends there too.