Fearful cat

We have 2 cats, but one of them is extremely skittish. She will only allow us to pet her if we are lying down horizontally, or else sitting next to her on the couch. Otherwise, she runs away in terror. She is four years old, an indoor only cat. We really wanted a friendly cat, and our other one is somewhat friendly, getting friendlier, but not this one. Can anything be done to make her not be afraid of us?

When I brought my first two home we had the same problem, they would only come near us if we were laying down, I think they knew humans are awkward and slow so they would have time to run away if need be. But we patiently sat on the floor with them with a stick and a string on it attached to a rubber spider and we'd swing it back and forth, nice and easy, eventually they would come over and start trying to swat at it. A little while every day. Your at their level being on the floor so your not towering over them. It takes time but eventually they do start to trust you. Now my two are all over me no matter what I'm doing. It takes a lot of patience. Good luck