Jill pulled the gun on an age function. Jill was thinking that some how maybe making Sue younger would solve something, but the gun was making her younger and Sue older. The rate of change happened quickly and she deaged quickly along with Sue who was aging quickly. Jill's breasts sunk back into her chest as she undeveloped and turned into an infant. Sue however grew bigger and matured a bit older than her normal age, but her breasts were much different. They grew bigger than usual and were still filled with milk thanks to those weird pills.
Jill stopped changing when she dropped the gun thanks to being a baby.
Sue went over to Jill, took the gun, and said "Now what should I do with you?"