"Mirror, mirror …"

Give her a bit more junk in the trunk.

Nothing like a fine set of glutes to go with fantastic formula muscle.  8)

I'm assuming it was just a sip that did that?

Then yeah. She should gulp it all down. ;D

I agree.  She needs to go to 7-Eleven, get a "Big Gulp" Cup, fill it with serum, work out heavily with what muscle she has already, and satisfy her thirst with the "Big Gulp" of Serum.

If I remember correctly, a Big Gulp can be as big as 64 ounces.  I think, or maybe 32, something.

Great work as always.

Yeah, I'm gonna chime in with the "she only had the tiniest sip, now GULP IT ALL" sentiment.

Great pic, made awesome by the promise of a continuation!

Maybe, if she selectively enlarges "her lower body, from waist downwards"

She looks distinctly top heavy at the moment…

Here's a suggestion to a continuation of the story. (Added some of the comments):

Glad that the formula had worked and that she had surprised her neighbor, she was now admiring herself in the mirror. But she wasn't satisfied. For starters she wouldn't mind having more "junk in the trunk". She wanted more and filled a 7-11 64 oz. cup which she drank knowing that the formula would change her. She wanted the neighbor absolutely floored by her appearance. She was however unaware of how the formula actually worked…

After she had gulped down the rest of the formula determined for more change, for more growth. She looked in the mirror and noticed her behind was filling out. It seemed as though her her lower body was being selectively enlarged from the waist downwards. At first she was pleased but then she wanted her chest to fill out to even things out. She giggled at the thought, ridiculous as it was, of her breasts filling out to the floor. Her breasts started to grow and strain the material of her shirt. And suddenly they pushed to the floor and actually started lifting her off the floor.

– Oh dear, she thought. This is too much!

It seemed that the formula affected the area of her attention. She then played around with the idea, focusing on becoming taller, then growing her arms out massively, stretching out her legs, thinning down her waist and making herself even bustier. Finally not knowing how much more time she had before the changing effects of the formula ran out she concentrated on what she really wanted. Remembering the women she saw in her neighbors copy of "Busty Amazon Body-Builders", she decided she wanted to completely dwarf them. She wanted her neighbor for herself.

Instantly she grew. Her arms, legs, neck and waist stretched out until she was twice as tall. Then she began filling out everywhere simultaneously , however her arms expanded at a slightly faster rate and her chest did so even faster. The end result was a Busty Body-Building Amazon of proportions nobody was even close of.

– WOW! she exclaimed, clearly stunned with her new lean massive body. Maybe I should make more formula and share some with my best friend. Or maybe it would be fun to try it out some more first.