Unless you have a proper *****es box set up a ***** that is not desexed will find a way to get pregnant. It is a biological imperative same as it is for the neighbour's male dog. There is no point in blaming a neighbour or the people down the road for having an entire male. The male dog is driven by the same biology as females and the most placid lazy male will find a way out once he gets a whiff of the sexy hormone smell.
Maybe the OP had no way of knowing this but she does have the option of ringing her vet today and getting her ***** spayed. Did the know that the full cost of a female desexing is in the region of $600 but most vets feel so strongly about it that they subsidise a lot of the cost?