Felicity hesitated a little. "Well, he's got this ... sort of medical problem, and this potion helps him out with that. It really isn't my place to elaborate though," she admitted. Because any way she could think to describe it would make it sound like her friend had a weird case of male PMS.
"It's a magical medical problem," she said after a moment, realizing that typical medical issues could be treated with Muggle medicine and she wouldn't need to make a potion.
"It's a bit complicated to make, but if we find everything I'd need for it, I'd give it a go."
Smiling, she pushed back from the table. After bussing her tray, she retreated to the table to pick up her list. "Ready when you are." She said brightly.