Dry humped with girlfriend 12 weeks ago, *** on underpants, is she pregnant?

She tells me now that her abdomen, around the belly button, is getting kind of firm. She had a period 6 weeks ago but is now around 12 days late for the current one. she has no nausea or tender nipples, nor has she gained any weight except around 2 lbs. no frequent urination either. only a firm belly.. help please is she pregnant?