referring to friends as Aunts/Uncles

I have a friend who wants to be called "Aunt ___" by the baby. I am not comfortable with this. My husband and I want to use those titles for our direct family. Another friend told me to let them know what the baby will be calling her (I'm thinking uuuh your name lol?)Anyone else experience this or have advice on the best what to tell them no?   I'm thinking the best way is to be direct : " we decided to only use those terms for direct family", etc...