That's a way to permanently stop Dinah calling Rosita 'Rosie'.

"Hey - I'm sorry." There's a beat. "I think Rosita's pretty. It's better than Dinah anyway. All I used to get as a kid was, 'You want fries with that shakes, honey?'" She chuckles.
"Back home, I was Canary, but here, it's always Di or D."