My cat is getting curious about the outdoors. =(

My cat, Kitty has been indoor only her whole life. She spent 3 months at a home filled with cats, went to a shelter, and then directly to my home. She has no idea of the dangers of the outdoors. I live in an unsafe neighborhood where cats have gotten run over many times.   many stray cats i grew to love that ended up dying.

Anyway, lately when she sees a door open, she'll lightly put her foot on the threshold. Like she wants to go out.

I usually shoo her away. But im concerned she will try to get out. Shes 4 years old now. She has another cat to keep her company. 

How can i deter her from wanting to go out?

I've thought about a catio or taking her for walks. But i worry that will encourage her to want to go out even more.

Take her for walks with a good harness. It won't make her want to go out more. I take Mingo out occasionally, and although he does sneak out from time to time, he's frightened quite a bit when he does get out. He crouches immediately and I pick him up. Cats are always fascinated with the outdoors, and you might be able to satisfy her curiosity by putting a perch next to a window. Cats love to spend hours looking out the window, and if you put a bird feeder outside, it's even better. Cat television. 

if your cat is harness trained, and you're patient, there's a dirty trick that I pulled on a cat once that liked the outdoors a bit too much for her own good.

Take your cat for walks... whenever the weather is BAD.  Rain, snow, severe heat, etc.   Don't torment your cat, when he or she wants to go in, oblige, but after enough trips outside, where outside seems like an awful place, the cat learns that outside is a bad time and tends to be less interested.

it *is* a dirty trick, but it worked on an unusually clever and stubborn cat.    Just don't ever let the cat out in decent weather, or you'll undo the hard work.