
As you said, just like people!
Some bitches are 'bleeders', others keep themselves so clean you hardly notice a thing. Some get moody, other don't. And it can change from season to season. So no hard and fast rules, really.
Remember not to let her out of your sight (not even unaccompanied in your garden) for the next 3 weeks, keeping her on the lead if there's even the remotest possibility a dog might be around, then give her a good bath (and wash her bedding) to get rid of any lingering smell.
:)