lol thats really weird but dont worry, it wasnt out of "retaliation". dogs dont seek revenge like humans do. she probably just had to go to the bathroom really badly, or if shes gone on the bed in the past, may be confused that she isnt supposed to pee on the bed. dogs prefer peeing in high places (or on hills), and they like pourous things like grass, carpet, beds, etc. exercise also stimulates them to go potty, so since she had just been running around that could also have been a factor. so I wouldnt worry about her ruining the house when the baby comes!