What can I suggest to her? Recently she's gotten about 90% there after years of not coming anywhere close. But she "can't" go any further. How do you know if you don't try?
Anyway....
Its harder for some people more than others depending on how severe thier gag reflex is. You really just have to work up to it. I usually start on my guy when he's not 100% hard and then its easier to go all the way down... other than that just go for it....
I think it does have something to do with the gag reflex. A friend of the program, from a while back, who just loved to perform orally had no, and I mean NO, gag reflex. She is the only girl I've ever been with that could deep throat or even really even got to the bottom half of my pee pee. If anybody has any insight, please feel free to post up. Unfortunately for me my current girlfriend does not enjoy the art of giving head.
Do not ever force it. It takes time and it will come. You make her happy and she will try to do the same. If you force it she will gag. They have to learn to relax and you can not help that process.
It is all in the breathing technique and relaxing your throat muscles and of course practice makes pros, but she has to be in complete control of the situation.