Audrey and Lina
Audrey just grinned. She'd had quite a few customers who were skeptical at first, but the sparkling milk--it actually sparkled. Twinkled. Glistened. Something about the milk reflected and refracted light--won them over in the end. It wasn't carbonated, but it glimmered.
"Ah, to have the metabolism of the young." Audrey teased, giving her new friend a wink. That's what they were: new friends. All her customers were friends. She set about her business behind the counter, warming up the muffins and making the latte, then came back over to the register to ring the younger woman up.