Hi Trev,
I can understand why you would resent your stepsister trying to move into a mother's role with respect to you, but I doubt that she really wants to do that. She sounds like a pretty savvy woman and I doubt she would aim for something like that. But...it is up to her to establish some guidelines and rules.
On "stupid fucking rules", yep, I understand what you mean. You feel you are old enough to decide most things for yourself, and when she interferes it drives you crazy. But every household has rules, and in every home there are rules that teenagers are expected to follow. Being told about the rules doesn't mean you are being treated like a little kid, it just means that the adults expect you to follow certain guidelines for your own good. And sometimes it's just a matter of courtesy. My parents, for example, still have rules in their house, and when I am there I try to follow them, even though I am 57! And it doesn't do me any harm when I do that.
Teenagers of EVERY generation hate these rules; I know I sure did. But let me tell you something. Just last week my daughter (she's 18) called me from Cyprus. She had been evacuated from Beirut and had made her way - alone - from the evacuation point, to the ship, to Limassol in Cyprus, to Nicosia by bus, and then two days later to Paphos, a beach resort where she is now relaxing on the sand, working on her tan, and meeting new friends.
Want to know what she told me on the phone? She thanked me for all those years of stupid fucking rules. When push came to shove she knew exactly what to do, how to take care of herself and how to manage on her own in a strange country where even the alphabet (Greek) is different.
I guess the point would be that rules aren't imposed on you to limit or control you, but rather to give you a useful working framework for the rest of what you are doing.
Much love,
Larry