Karen giggled a bit more after Haley left, knowing how shy people were and how they eventually come out of their shells. She giggled some more and after a while fiddling with her hair subconsciously, finally decided to stand in front of the mirror Haley was in front of before. She looked at herself for a while with her tongue poked out in thought. She poked and pulled at parts of her 'costume' for a while before turning around and inspecting her back. She continued pouting and started mumbling something while she continued poking around.
[color=red]"B-U-T-T... Butt... Beepity boopity bop... B-O-Y-S... Blepity blopity boop..."[/color] Obviously if anybody could hear her they'd either see Karen as playful or childish, or completely insane. It was an innate mind-set she was in, only really understandable if someone truly knew her. Eventually she stretched once or twice in her costume, then turned on her quirk for the first time since her arrival at UA. Her entire body was coated in flame, and her costume was lost in the intense heat and fire. Almost all details of her body is lost in the fire, barely even her body outline visible while coated in the fire and the flames. She clenched her fist and held it out in front of her to look at, and as she did so, all of the flames around her body intensified, both increasing the temperature in the immediate area, and slightly scorching the floor of the changing rooms. She laughed, then looked in the mirror for the moment of truth. She deactivated her quirk and stared at herself in the mirror, the costume being singed, but still functional. 
[color=red][i]Damn, gonna have t'make it more resistant. I'll make a note of that somewhere, sometime, probably not.[/i][/color] She then nods to herself, and starts walking out of the changing rooms, either bumping into her partner or not, that being up to the GM.