A. As she is unspayed, she might have developed a uterine infection (Pyometra). The uterus fills up with pus causing a life threatening condition.
If this is the case, this is an emergency situation, you need to take her to the vet immediately to get it checked. The vet will either confirm it or rule it out. If it is confirmed the treatment is surgery in order to remove the uterus ASAP.
She might need to stay for hospitalization for a day, depending on her recovery.
Your account has been reactivated.