I googled "gila monster" and have the impression that's what it might have been! If so, they are venomous. We used to let our cats outdoors, but eventually decided they are just safer as indoor pets. Your cat looks wonderfully healthy, especially for her age.
We have little anole lizards here, and our previous cats preyed on them. The vet told me that for unknown reasons eating the anole lizard causes wasting in cats. He pointed out that if we could figure out what does it (and if it would work for people), we could bottle it and get rich!