I know we ascribe all sorts of human feelings to our dogs, but I think malice and revenge are a bit beyond a 3 mo old puppy. Even the best housebroken dogs have 'events'. My 4 month old peed twice in the house the other day (after being out), and that was a first. Both spots were ones where I clearly didn't get out old 'event' odors from the big dog who had the runs one day quite awhile ago. I wondered if my puppy might be getting a urinary tract infection, but since that was the only time this happened, and he seems fine, I guess I can rule that out. I hope your little one doesn't have any repeat occurrences, but if she does, try and catch her in the act, tell her 'no' matter of factly, and immediately bring her outside to a 'pee' spot.