My girlfirend can wear it at home sometimes but almost never when we are out.
Why would she wear it at home?
I've exchanged some e-mail messages with a young Muslim woman from Indonesia (a religious one - once when we were chatting she had to take a pause for her prayer) and it was a very nice experience. We talked about our countries, a bit about history, food, she sent me some recipes on how to use batatas because I bought some at the supermarket and didn't know what to do with them lol
She was very nice and friendly and it felt not much different than talking to a religious Catholic girl from Poland, tbh.
Considering your girlfriend doesn't even wear a hijab I don't see a problem, as far as her looks - she will have no more problems then, let's say, the Vietnamese would (if they have any), I suppose (?).
In which city in Poland would you like to live?