The vet said 5 months old, around Halloween. Today, for the first time, she made it over the half-doors we have separating one half of our house from the other. We divided it so the cats can have an area away from the dogs - so one doorway has swinging half-doors, and I clamped a mirror on it so she couldn't slip under the doors. Today, Hanna made it up and over - into dog land. So I called the vet, she's going in for her operation on Wed. morning.
I am still really nervous about her being out with the dogs. My dogs know not to mess with the cats, but they haven't had to deal with a five-month old kitten. Both my other cats were adults when they met. Bandit is old (12) and he doesn't like any cat invading his personal space. I will be here keeping an eye on them, but things can happen so fast. And there is so much more stuff for Hanna to get into in the main part of the house - I am going to be a nervous wreck.
Hopefully the spay will mellow her out a little bit - she is so mischievous.