About 3 months after it was given birth you can get her spayed .
Most vets want to wait until at least about 9 weeks after and the pups are weaned and gone (earliest they should leave is 8 weeks) if there isn't some sort of emergency situation. Give your vet a call and let them know the situation and you can set up your appointment based on when they prefer to do the surgery and you'll still be able to catch her before the next season most likely. Good Luck.