It is said that people who have betrayed by an A will have the hurt feelings lasting 2 years or more. She is going to have to understand that YOU are the one who was hurt and healing. Not the other way around.
How much is enough? That's not even a question. Only time is going to get rid of those insecurities. You are still living with the fear that she could do this again. That's just the way it is. SHE has to continue to reassure you again and again. Not the other way around.
Check out some of the sites online that deal with the healing of infidelity. survivinginfidelity.com is a great place to start.
There's a healing library on there that will explain what you and her are going through. It's not going to be an overnight change in attitude. If she is truly truly remorseful, she will go according to YOUR timeline, NOT HERS.
M-43 W-40 2D - 9 and 5
Emotion, yet peace. Ignorance, yet knowledge. Passion, yet serenity. Chaos, yet harmony. Death, yet a new life.