The bubbling was tickling Peter's nose, distracting him a bit. So that may have been the reason he missed the slight growth in Joce's chest at first. But after a minute or two, he noticed the sound of stretching fabric, and was presented with Joce's top growing wider and wider as two globes pressed it out from the inside.
When he reached out to put his hands on her growing sides, the expansion began to pick up speed. Joce threw her head back and moaned a bit as a high pitched whine, then snap, signaled her bra being overwhelmed. Peter stroked as her breasts as they were soon large enough to brush her waist.
Finally the shirt began to lose its fight, and tears began to form all over, revealing the soft flesh underneath to him. With one last rip, both Joce's and Peter's lap was filled with boobs.
Joce gazed at her overwhelmed boyfriend and let loose a happy sigh. "Like 'em?"
"Well, yeah, but you're huge!"
"Huge?" Joce feigned innocence. "Oh these are downright tiny..."
"...Compared to how big you're gonna be."