V.S.
I'm going through the same thing with my second son (also 3). I have an 8yo and have been through this before.
Its not you or what you are doing its just the age. Some kids go through this.
Keep doing what you are doing, she will get it eventually. Also keep trying to get her out and around other kids. Join a playgroup or meetup with friends who have kids the same ages. More interaction can only help.