Neither Potter's nor Snape's spells hit their target. Potter's wand was knocked away by a spell, but at such close range, before Snape could cast another proper attack, his wand was knocked away by Potter's flailing arm. The wandless pair quickly devolved into rolling around on the floor, while Evans stood at the side, trying to pull Snape away.
Lys muttered irritably to herself, "Why don't you pull Potter away instead, Evans? You're just hampering Snape's performance!"
The Hair-Growing Charm and the incomplete Cheering Charm were slow to take effect. After Sirius Black's spell went awry, he didn't dare cast any more spells for fear of hitting his best friend. He tried to punch Snivellus directly instead.
But what was this? Wasn't this his favorite Muggle motorcycle? Delighted, he reached out to touch it, not expecting it to be so hot. Wait, wasn't he supposed to be helping James deal with Snivellus?
Shaking his head vigorously, though something felt off, he still felt strangely elated. Haha, my brother James can't lose! Something was blocking his vision - oh, it was his own hair. Haha, my hair looks so beautiful.
Both Lys outside the door and Peter standing nearby could tell something was wrong with Sirius Black. Lys crouched outside, stifling her laughter, while Peter pointed his wand at the pinned-down Snape, squeaking, "What did you do to Sirius!"
The fighting and mediating parties all turned to look at Sirius Black. He was running his fingers through his now waist-length hair, wearing what could only be described as a maniacal yet satisfied expression. "Oh James, I knew you'd win. How could any friend of mine lose? Especially against a Snivellus, right?" He kept preening his hair as he spoke, making him look strangely familiar.
"Sirius, are you alright? Snivellus! What did you do!"
Potter didn't finish his thought about why Sirius looked like his mother - it was too disturbing, and gave him goosebumps.
"My friend is the best, Lily Evans, where are your eyes? Why play with Snivellus? If you can't make the right-"
"No! No! Sirius, snap out of it!" Potter quickly stopped his friend from finishing, not even noticing that Snape had reached for a wand, though Peter's constant vigilance prevented Snape from getting up.
Lys watched anxiously - Lily Evans was the only one with normal fighting capacity now. That Peter had been holding his wand forever without daring to cast a spell. Why didn't she just pull James Potter off Snape?! Tch, this was frustrating.
Lys wanted to intervene, but Potter's face was turned in her direction now. Any large movement would give her away, and she dared not cast unfamiliar spells - what if she accidentally set someone on fire or caused an explosion? She only wanted to make them uncomfortable, not cause fatalities!
Watching Potter land a solid punch on Snape's nose made her own nose twinge in sympathy.
After that punch, Potter stood up to check on his friend. "Oh James, don't worry, this is my favorite motorcycle, let's..." Seeing his friend becoming increasingly incoherent, with hair nearly touching the ground while grinning stupidly, Potter knew he couldn't delay.
Leaving behind a struggling, bleeding-nosed Snape, Potter retrieved his wand and helped Peter support the increasingly bizarre-acting Sirius Black. "Snivellus, you'll pay for doing this to Sirius, just wait!"
Pah! So you can bully others with spells, but others can't use them? Is bullying with magic your family tradition?
Seeing the three about to exit, Lys quickly ran around the corner. She really hoped there would be lots of students on the way to the hospital wing to laugh at Sirius Black.
She thought that would be the end of it, but the next day at the Great Hall, Professor Slughorn, wearing an odd expression, called Lys to the hospital wing office, where Madam Pomfrey and Professor McGonagall were waiting.
Lys blinked but remained silent. McGonagall nodded to Slughorn and asked, "Miss Starlys Black, we've called you here hoping you'll truthfully tell us," she pointed to a bed outside, "if you're responsible for the spells affecting Sirius Black?"
Lys stood silently for a moment before asking, "Why are you so certain, Professor McGonagall?"
"Because the Hair-Growing Charm has gradually turned his hair silver, and the cauldron stand in that classroom also turned silver. I believe one of your spells didn't fully hit Sirius Black, did it?"
Lys could barely resist slapping herself. Tch, caught red-handed.
"That's because..." "Oh child, regardless of the reason, even if Snape and he had a conflict, it should be resolved between them or through professors. You shouldn't have intervened."
Slughorn impatiently interrupted her, "Slytherin loses 20 points because of you, and you'll serve one month of labor service. Now you need to apologize to the Black family's eldest son." He pushed Lys toward the hospital bed.
Sirius Black lay quietly in bed, looking quite healthy with rosy cheeks. Lys stood there, watching his smug expression. Her planned apology transformed on her lips into:
"Your mother doesn't want you either!"
Sirius Black shot up from the bed in anger but pulled his ever-growing hair, hissing in pain.
"I won't apologize to him! I was in here for a week and he never apologized to me. Even Snape, who was also a victim, though he didn't apologize, at least sent me an apology gift. But this person? He even mocked me afterward!"
Though Madam Pomfrey felt the boy in bed was wrong too, she still said to Lys, "Lys, spell damage is most complex and unpredictable. You shouldn't have done this."
"It's not unpredictable. I tested both spells on myself! The results were very similar, except for the color change." Lys stubbornly refused to back down.
"Slytherin loses another 10 points for your disrespectful and dangerous behavior. Your labor service is doubled. Child, I hope you recognize your mistake." Slughorn looked extremely displeased at Lys's defiance.
But his displeasure at the point deduction vanished upon seeing Sirius Black opening and closing his mouth wordlessly - ha, a side effect of the spell.
As the professors discussed how to treat Sirius Black, Lys was allowed to leave the hospital wing, as the two children were glaring at each other, and the one in bed looked ready to jump out.