I'm 22 (geez I just turned 22 two days ago and it has not sunk in yet) and I think to a certain extent we should cut ourselves some slack and not worry too much about what we're supposed to do as adults. Everyone does things at their own pace. As long as you're striving to do the best you can and be as independent as you can in your circumstances we shouldn't stress too much about it. I say this because feeling mature and independent is something that I struggle with to the point of obsession (a large part of this stress stems from the fact that I am deathly afraid of driving) and I know I personally should be easier on myself in that regard.
Happy Birthday! I turned 22 at the end of July and it definitely still hasn't sunk in

I'm 100% with you on this - it's a weird age where you simultaneously are an adult, you've lived fairly independently for a few years if you went to uni, you may be getting a job, you may be carrying on studying, but you're also still not quite sure how the world works, and you probably haven't figured out yet exactly who you are or what you want to do. At least I hope that's normal and it's not just me having a mild identity crisis lmao. And everyone is at different stages of development. A couple of days ago I went on Facebook to discover that someone in my year at uni, who I had multiple classes with, is fucking engaged. This has happened a couple of times now and it honestly gives me the biggest shock every time. I've never even had a proper boyfriend lmao how the fuck are there people my age settling down

It's fine though, because I have no interest in dating, and I know she and her partner have been together years and are very much in love. We're at very different stages of our lives in that respect, and that's okay because we're both doing what's right for us. The thing that worries me with Ruby isn't that she's not doing certain things, it's the reasoning behind it. If she doesn't want to drink and party and have sex that's fine, lots of people don't enjoy that kind of thing and it says absolutely nothing negative about her as a person. But if the reason she avoids that stuff is because she thinks people who enjoy them are in some way intellectually inferior to her, that's different. To figure out who you are, you have to step outside your comfort zone sometimes - that may be with how you spend your time, what you read or watch or listen to, who you spend time with. Just anything to widen your perspective on the world. If you enjoy certain 'childish' things, but are also able to engage with the real, adult world when necessary, and know that ultimately you are an adult, that's fine, you do you. If you hide in those things as a means of avoiding facing adulthood and adult issues, that's slightly different. Ruby will never figure out who she is if she never attempts to broaden her horizons in any way, and just pretends to be a child for the rest of her life.