"Oh, I wouldn't be so sure about that. Just one sec!" Trini exclaimed arrogantly, looking down at her far too tiny sister.
"I wish I was 21 years old!"
And just like that, Trini matured in front of her once big sister's eyes. She didn't grow at all in the height department since she was already 6'2" tall, but made up for that in pretty much everything else. Her face went from cute to down right sexy, obviously much prettier than Sam ever was. As if that wouldn't be enough, her boobs were full DDs despite her muscular body. Her ass filled out nicely as additional muscle mass was flowing into it while her waist shrunk a bit.
"There we go, now you aren't even the older one of us two!" Trini said, telling the obvious
"That's not fair! Change me back to normal you big freak!" Sam said in fury.
"Didn't I tell you to be nice to me? Apparently you don't want to grow some like me. Speaking of which... I wish I was even taller, more muscular and stronger!"
Trini stuck out her tongue and waved at her tiny sister and she began to shoot upwards. While being over six feet tall as a woman was already quite impressive, Trini aimed much higher. She easily crushed the seven feet mark, stopping at about 7'5". Trini was huge now for any normal person, but to Sam she was gigantic! She was now eye-level with Trini's hips.
Just as she thought it couldn't get worse, her muscles started to grow as well. Her big 15 inch guns quickly expanded several inches until they were 22 inches around, absolutely huge! The legs that were just in front of Sam each grew wider than she was by a good margin. Her strong core of six infividual blocks of muscles gained two more friend, bringing her to a mighty 8-pack. While her shoulder grew wider and bigger, her waist seemed to stay about the same size. Sam was agape. Her bratty (once little) sister possessed far too much power now.
But that wasn't it. After her muscles were done growing, Trini felt them change, but not grow. When she said "stronger" she didn't really mean it, but that's what she's getting now. And a whole lot of it. She felt all of her muscles densen, the feeling was indescribable. But what Trini felt, Sam could actually see. She looked up at the abdomen and saw the 8 powerful blocks gain definition beyond belief. Even without her ever touching them they looked harder than stone, even unflexed. The same happened to the rest of her body as well, a whole lot definition to go with incredible amounts of pure strength. Trini was now far stronger than she looked. And she looked pretty damn strong already!
"Now that's more like it! What do you think?" She rhetorically asked, resting her slim but powerful fists on her wide hips.
"You're crazy, Trini!"
"Not crazy, big! Honestly, the way you look at me now is the same way I felt when I looked at you hours ago."
"This isn't even comparable, you dickhead!"
"Insulting me again? Alright, you asked for it. I wish Sam would be one foot shorter and I would be one foot taller!"
Sam's heart stopped for a second, realizing what was about to happen. Right as she felt that same feeling from a couple of minutes ago, Trini felt the same, but better. As Sam was dwindling further in size, Trini skyrocketed further towards the ceiling. Sam was now 2'2" short while Trini absolutely towered above her at an astonishing 8'5". Sam was now eye-level with Trini's knees rather than her hips.
Sam had to look waaay up now in order to see her bratty sister's face. And bratty it was. She looked down at her once big sister like an insignificant speck, all at her mercy alone.
"Was that all you had to say to me, you little shit?" Trini asked, clearly angry on the outside, but inside the was savouring the feeling of power over her sister.
"..."
"Thought so!"