Cats can get used to almost anything if you do it slow and they think it's their idea

. I would start very slowly introducing the leash, maybe give her favorite treats at the same time, lots of love and praise. Maybe open a window and put a chair or a cat tree next to it so she can equate the outside air and all it's pleasures with the leash. Just kinda work up to it.
I used to compete with purebred cats in championship cat shows. I gave them 7-step bathes and blew them dry with an industrial strength blow dryer. I trimmed their eyelashes and shaved their nose leather. Then I took them to the airport, took them out of their carriers and walked through security with 1 or 2 cats in my arms. Their carrier went under my seat in the airplane. I made several trips to France, Austria and Switzerland with my top show cats.
In my 10 years of showing cats, I saw many cats on leashes and they loved it. I have cats that fetch and beg like a dog. I have one cat who grabs my hand with her paw and puts it on her head so that I will scratch her head!!
So, you absolutely can teach a cat things, if they think it is their idea and they really love to do it.