idk how to handle it ...

Soo... I am 36 weeks pregnant with our first child. He will be named after his father who is a junior; therefore, he will be the third. His family all has nicknames that they call each other, so we decided very early in my pregnancy that his nickname will be A3. We wanted something different, and I specifically did not want anyone calling him Trey as it is a very common name. & to me... if I wanted my sons name to be Trey then I would have named him that. It’s not really a nickname to me. But anywhooo.. my soon to be mother in law insist that A3 isn’t a name and she will call him Trey. I personally feel like it’s disrespectful. As his parents, we decided on A3. & I feel if someone doesn’t like that nickname, they can call him by his real name.. We both have expressed to everyone in the family on MULTIPLE occasions, including her, not wanting to call him trey. She’s not the type to care about other peoples feelings towards things, so I don’t know how to handle it... and it might sound silly but I just really do not want him to be called Trey 🤦🏻‍♀️