We have had sassafras now for almost 2 weeks but she still hides in her shell when I am by her. When or will she start to relax and be the personable sulcata everyone talks about?
Give her time. Older ones sometimes take longer then younger. Specially if they didn't have the best of life before you rescued her.
Oh and not all become friendly and personable.
I am not good at guessing age. It is very hard to do as they all grow at their own pace. So much depends on how they were hatched and raised. Post a pic if her next to something for a size comparison, like a quarter or next to a tape measure and someone might be able to give you a possible age guess.
Get a good weight and measurement on her. It really depends on how she was taken care of previously. She looks good. From what i see without any measurements or seeing her she looks to be around a year old...as far as her being shy, the best thing i can tell you is do what you are doing and talk to her when ever you are near her and when you soak her talk to her and try to rub her head...she will warm up eventually