So far she can gain muscle without gaining an inch and learn how to grow to over a hundred feet tall without gaining extra muscle resulting in a gigant version of her once small, skinny self. It's amazing what you can do with quantum immunity and not have to worry about such silly things like the square-cube law and bio-structural compromise.

So far Mercedes needs all the space she can get because it's bulking day. She will learn how to make her muscles as big as she can as fast as she can. That's where she'll learn her "Musclebomb" move later.

Art (c) Cybercat