Welcome to JustAnswer! I am a licensed veterinarian and would be glad to help!
Knowing that she is spayed - I would first evaluate for problems such as UTI.
If there is no UTI, then I would consider an ultrasound to make sure there is not a stump pyometra (an infection of the remaining portion of the uterus from the initial spay procedure)I hope this information helps!_____________________________________________________________________Please click "ACCEPT" if the information I have provided has been of help so I receive credit for my work. Bonuses are always welcome and appreciated. Thank you.The above is given for information only. Although I am a licensed veterinarian, I cannot legally prescribe medicines or diagnose your pet's condition without performing a physical exam. If you have concerns about your pet I would highly advise contacting your regular veterinarian.