She holds an Amortentia potion up to your face. It's the potion that smells like what attracts you.

I need you to take a few sniffs of this, please. -Oh, and tell me what it is you smell!

There's a few boys standing close by that happen to know what's going on, and they secretly get a bit closer to you and Hermione to find out what it is you smell in the potion, and who it is you like.