First, I should consider the context. The user mentions "m new," which probably stands for "my new" something. Maybe the sister's presence is causing issues with something new the user is doing, like a new project, social environment, or perhaps a new group of friends. Since the user hasn't provided specifics, the post needs to be general enough but still clear.

That said, I truly value our connection and hope this doesn’t change the good times we’ve had sharing other parts of our lives. I hope you can see where I’m coming from, and I remain grateful for your friendship.

Let’s keep things light and positive where we can—thank you for hearing me out.

Dear Nicolette,

I should structure the post in a positive and constructive way. Start with a friendly greeting, state the request politely, explain the reason if possible (without giving too much detail), and close with appreciation for understanding.

Possible phrases: "I hope this message finds you well..." "I need to set a boundary..." "I appreciate your understanding..." "It's best for me if..." Maybe also mention that it's a personal choice rather than a judgment.

They might also want to avoid any negative connotations about the sister directly. Instead of saying something like "your sister is a problem," it could be phrased as a request based on their own needs or circumstances.