What are things that mature women want in a guy/ Relationship?

Lately I've been talking to this girl that is extrememly intelligent we have dated before and split up because I left her years ago now I'm back and she's completely changed mostly because she matured and experienced events that she will not talk to me about for good reason. I don't give her secrets away to people but I just want to understand how to better understand somone that has had a traumatic past and will hardly open up to those questions that I want to know and be more mature for her since I have been bombarding her with messages or I feel like it. I just want things to be the way they used to be when we were dating were she told me everything but she won't because she still views me as childish. how do I grow up and give her what she wants, what do most girls look for in a more mature significant other? she's practically the only girl that I've ever talked to in my entire lifetime so It's hard for me to change when I have a hard time talking to girls in the first place. She's my first love and my first real girlfriend so I feel as though I owe her that but does it just come down to being myself and not trying to be somone that I'm not? or is there something more to this that I'm not getting at?