I would suggest your gf take a pregnancy test to find out for sure. If she skipped the sugar pills to miss her period she may just be having a strange bleed because of it. This happened to me once when I was on the pill. One month I skipped the sugar pills and still got some slight bleeding, but it was off colour to a normal period (i.e brownish and pinkish).

Definitely take a HPT if you want to know for sure. Best of luck!