Hello Susi and welcome to our family, we are so glad you found us and we look forward to hearing more about you and your grey.
She might have been a wild caught grey since she still does not want to have any contact with you since you have had her and you have had her now for 6 years, thats a long time to not be able to get her to step up for you, she should at least be tolerant of your being around her. I am afraid I am at a loss as to what to tell you to do, I have never been in your situation before and we may have to get some of the more knowledgeable members to give you some advice.
You are doing what you should be doing to earn her trust but she may be happy just the way she is, some do not want any touching and she obviously doesn't so you may just have to accept her the way she is.
You could try to get her another mate but she may not be so accepting of another one so hold off on that idea until you hear from some of the members here. When you deal with rescues you never know what you are going to have to deal with and they bring baggage with them that they never fully unload.
You may find some helpful advice in our many threads so do read thru them and ask questions you may have and we will help you in any way we can.
We would love to see some pictures of this grey if you have some you would share with us, btw, what is her name?