Usually even if they have wonky cycles, they will start to cycle normally after they have a litter. Odd that she started having irregular cycles after she whelped. How many heat cycles did she have before she was bred? Were they always 6 months apart before this? Sounds like she is coming in or could be having a split heat. Take her to the vet, get her cleared and schedule a spay. Contain her properly to make sure there are no more accidents. I have had multiple intact females in the same home when they were in heat with my intact male. I had no accidents because dogs were kept properly contained. If you have an intact animal, it is YOUR responsibility to keep it contained so you do not have accidental litters. It's irresponsible. I'm glad you are getting her spayed. Please contain her this time around.