Welcome, Jill. God bless you and Molly! She sounds like a precious joy.
You are doing the right things to gain her trust. Identify a treat that she LOVES. Stop serving it in the cage. From now on, let it only come from your hands. Break it into bits, if you can... such as cashew bits or peanut bits... or one sunflower seed at a time. This way, you can reward her with treats often. Spend as much time by her cage as possible, talking to her and telling how much you love her and want her to be happy. You can create talking games or anything like that, too.
When she is ready for the head scritches, give her a few gentle ones with your fingers thru the cage bars. Give her treats, too. Again, make up talking games and so on. But the physical contact should go slowly, one step at a time. It would start with the head scritches through the bar. Then when she loves that, slowly try the head scritches with cage door open. After that you can play foot games with her. I used to play a game with Kyo where I would touch his foot and say "Boop!" Then, he started saying that. Now, I massage his feet. But the physical contact should come slowly and with a positive reinforcement strategy of one inch at a time.
Congratulations! You have a beautiful future ahead of you with this beautiful soul.
Blessings,
Maggie-
PS: Many of the strategies that are used to work with phobic/nervous greys would work. They are basically what you are doing. Just remember to go at her pace.