I have a female Jack Russell Terrier that came in about every three to four months. Vet said some dogs just do that but we had her spayed because twice a year is bad enough but everytime we turned around she was in again had to put a stop to that fast. So it maybe possible but then again just to be sure something else is not wrong take her in to see that vet. Oh by the way she hasn't been around any other females that are coming in has she?
Rhonda