Sorry blent, you're generalizing and assuming a lot. I was dating a woman who was 36 when I was 18 and there were no maturity issues. Everyone is different and perhaps he thought that she was more mature than she actually was/is. People who are younger shouldn't automatically be written off because of their age. He gave her a shot, and it isn't working the way he'd hoped. I don't say that to slight the OP either because you can only be who you are and can only work with what you have. She sounds like she wants to be more mature, but that is something that no one can hand to her or teach her. Only time and experience can do that.
...one can be sure of nothing until it has already happened...