Not knowing both sides of the story I can’t speak to your exact situation but I can say that we’ve been dealing with this with our son for the last six years or so. He’s also of the opinion that his age automatically brings with it some sort of change in status. I’ve often told him that I can write “Dr.” in front of my name all I want; that doesn’t mean anyone’s going to let me operate on them. Just because someone has the legal status of an adult doesn’t mean they have any idea of how to behave like one. I’ve also found that young people who claim they want to be treated as an adult often don’t want that at all. When my son took a bunch of time off to go see a string of concerts, then blew the paltry paycheck that followed on junk food and soda to enjoy during the marathon gaming and cartoon-watching session he had with his friends, his idea of being treated like an adult was for us to cover the bills he suddenly couldn’t afford to pay. When we instead treated him like an adult–that is, we let him fend for himself–we were suddenly mean, horrible parents who didn’t love him or care for his well-being.
The fact that you’re saying you expect to be treated like an adult because you reached some arbitrary milestone as opposed to having changed your behavior by presumably becoming a more mature and responsible person leads me to believe that your attitude about adulthood is similar to my son’s. The things I had at his age that he doesn’t have include a house, a wife, a son, a college degree, a car and a full-time job. I’m not saying those things are necessary for being an adult, or that having those things makes one an adult, but certainly the capability to be responsible for those things is a big part of being accepted as an adult. Acting like a child and watching kids shows certainly doesn’t give one the veneer of an adult. And, yes, we’ve dealt with that plenty with our son. Whether it impedes on his other responsibilities or not, him telling us he spent an entire day in his SpongeBob jammies watching cartoons and eating Fruit Loops doesn’t leave us with any confidence that he’s going to make it to his job interview the next day, or pay his rent, or get his library books back on time, etc.
I guarantee that, for as often as I use the phrase, “Act like an adult and you’ll be treated like one,” I sound like a broken record; however, it’s absolutely true. If our son spent a month, or even just a week or two, meeting every one of his responsibilities without having to be told, waking up before noon, shaving, grooming and dressing like someone with some goals and objectives instead of like a four-year-old on Saturday morning, he might get treated a little differently, not just by us but by every other adult who has to deal with him. Even if he just spent a month fending for himself and fulfilling his obligations on his own, that would garner him a lot more respect and adult-like treatment. Until that happens, though, our gut reaction in every situation will be to expect the far-less-than adult behavior he consistently displays. Perhaps if you didn’t show your mother the childish behavior you admit to having, she might reexamine how she deals with you.