Guessing that they’ll just go with the “nickname” route since Bon Bon has a card in the TCG that has her and Lyra together.

Sweetie Drops?  
>inb4 sweetie bell’s real mom/sister/relative/whatever

What’s a sweetie drop? Where can I buy one?

Not calling her anything but Bon Bon.

So Bon Bon’s official name is Sweetie Drops? Not bad if you ask me.