It can take a really long time sometimes when it's just one new bird your trying to integrate. I no longer try to integrate single new birds, I've just had to much trouble with it. Just keep doing what your doing, letting them see each other but be separated by fence. Maybe put the new bird in the coop at night in a wire dog crate as well so they can get used to her in there to.
I will say, the last time I tried integrating just one new bird I did all those things for two months and they never did allow her in the coop and almost killed her the last time I tried. They finally got to where she could free range with the flock but she never was accepted into the coop.