Not TOO obvious to get her suspicious, but a few hints do need dropping.

That day, during lunch, Izuku got his meal from Lunch Rush, and joined a table with Ochaco, Momo, Tooru and Setsuna. "I never get tired of Lunch Rush's meals," Izuku remarked. "If my mom wasn't a good cook herself, I'd wish that I could have it every day," he stated as he sat, putting just a bit of emphasis on the word "wish," but not a blatant amount.

Setsuna looked up, staring at him for a moment, before deflating slightly. "Something up, Setsuna?" Tooru asked with a knowing grin, trying to hide just how amused she was.

"Nothing, just wishful thinking," Setsuna sighed. She seemed to think she had imagined the subtle emphasis on the word when Izuku had used it.

Ochaco giggled. "I know the feeling. I've wished that my Quirk didn't cause me nausea in the past," she noted. "Of course, it's not a problem anymore. Now I can have all kinds of sexy fun with it!"

"Wait, your Quirk used to cause you nausea?" Setsuna asked curiously.

"Yes, when I use it on myself, or just lift too much weight, it used to cause that problem," Ochaco admitted. "Then, after a while, it was gone, like magic!"

Setsuna blinked, before gazing at Ochaco suspiciously. "Magic?" she inquired. She slowly turned towards Izuku, the gears turning in her head as he grinned, a clear sign of mischief in his expression. "...don't tell me..."

"Hey, have you ever heard of the old American Disney movie, Aladdin?" Izuku questioned out of left field. Setsuna's eyes widened as her suspicions were confirmed abruptly.