1st heat cycle, vet says either Coton has a pseudo preg.or is pregnant

by Judy
(Buffalo ny)

Cotton behind 6 ft wooden fences with exception of 4 ft gate. Vet says either coton has a pseudo preg., or is pregnant. Going back for checkup 3 weeks. Coton does not leave house, or yard, except groomer or vet visits. Vet said pseudo preg is unusual for coton in 1st heat cycle, however, she stopped spotting blood 1 week ago, and vulva still enlarged, and mammery area feels "full". Coton gained one pound in a month. Is it really so unusual for 11 month old coton to have pseudo on 1st heat?