As it turns out, Elphaba redeemed her 'owe you one' a few days later.
"A little fog isn't going to kill you!" Challenged Galinda.
"It very well might, seeing how I can't find any of my legwarmers!"
"It's not even supposed to rain!"
"Rain, I can hide from. Humidity creeps into everything!"
"Soggy clothes aren't the end of your life! Your social status, yes. But not your LIFE!" Elphaba stood glaring for a moment, then dragged the smaller girl into their shared bathroom. She took out a hand-towel & swiftly turned the water on & off, once. She yanked the other girl closer to the sink, and gritted her teeth. When she was sure the other girl was watching she thrust her hand under the dripping faucet, holding her breath so she wouldn't let out a sound of weakness. She held her hand there for quite a while and Galinda was unsure weather to watch her unbreathing roommate, or water's effect on said girl. After watching the green face slowly darken with need for oxygen, she glanced at the hand and saw red drips running off of it, down the drain.
"HOLY SHIT! BREATHE! GIMME YOUR HAND!" She yanked the green hand out from under the drops, and carefully blotted it dry with the towel, as the green owner of said hand let out her breath in a long, low hiss. Galinda couldn't believe it. She put her finger under the dripping water, then her hand, then she filled a cup and drank the stuff that had caused the school joke to bleed. She felt fine.
"Miss Galinda, could you assist me?" The blonde ran into the other room, expecting to see a red stump where a green hand should be. However, it was just Miss Elphaba, attempting to bandage herself with one hand. She knelt next to the girl and helped her, just as their roles had been switched not even a week earlier. Galinda put salve on Elphaba's uninjured hand, watching her rub it on the wound. (She couldn't make herself touch the green girl's blood.) She then took the roll of fabric and wound it around the green palm. Once that was over, her senses came back.
"What in OZ was that for?!" Galinda shrieked
"Now you know why I can't go out when it's wet. Please tell your friends to return my leggings." Elphaba responded quietly, looking at her bandage. "Also, please bring my homework once school is over, I can't fall behind." Galinda gaped at the calm of the wounded girl. "I'll certainly tell our teachers you had an allergic reaction and are resting for the day, but WHY would I bring you back your schoolwork?"
"3 simple words, my sweet. You. Owe. Me." Galinda remembered the soup of a few days ago.
"Fine, fine. Get your work from the teachers, anything else?" Galinda grumbled. If any word got out about this she'd never live it down.
"I'm going to need to copy your note... never-mind, just the missed work."
"What about lunch?"
"What about it?"
"You obviously can't go to the cafeteria, what should I bring you?"
"Dear girl, I've missed meals before, I'll miss them again." Galinda didn't like this response, her roommate was already all sharp bony angles. Galinda didn't want to come back to the dorm to find a malnourished green body, and be blamed for starving her roommate. Of course, she didn't say this aloud, Miss Elphaba had a logical mind like no other, and she loved to play 'Devil's Advocate'. Galinda's argument would be tattered shreds before she even opened her mouth. So she simply made herself a promise to bring Elphaba's lunch back to the dorm.