[SWHouston]

Not is it just difficult, but sometimes impossible to tell if a Female has been Spayed (after a generous healing process), the scar can totally disappear, and even Ultrasound is not revealing.

I had this same situation with my Chi Navi, and my Vet insisted that we just wait, and see if she came into heat...she did.
It was a little PITA given I have two in-tact Males as well, but, that was much better on Navi and me, than an unnecessary encounter with the anesthesia and exploratory surgery, and taking a chance of a subsequent problem arising. Never the less, then surgery was indicated, scheduled, and Navi is back to her Bossy self (typical Fe Chi).

I was very glad that my Vet was firm about not doing anything, and just waiting to see if She would go into heat. There are several Vets at the Hospital I take my guys to, and, I don't remember if I have told them, how appreciative and confident I am in their advice, and apparent excellent care of my loved ones.

I'm going to make sure that I say something to them, the next time I'm there.