A, My Name is Ami — Norma Fox Mazer

The more things change, the more Ami wishes they'd stay exactly the same

Ami and her best friend, Mia, share almost everything -- even the letters in their names! But when Ami's mom and dad separate and her mom moves out, even all of the traditions she and Mia share can't put her family back together.
 
Ami wants everything to go back to the way it was -- for her mother not to live in an apartment and have a life of her own, and for her dad not to go to dinner with the new science teacher, Ms. Linsley. At least her friendship with Mia will always be the same . . . won't it?