I always run into ppl with brownies who say shit like "careful with these, just eat like 1/2, my friend ate one and tripped balls!" Whatever I've never run into a brownie and its friends who wasnt my bitch, but then again i'm a pretty huge head. Get ahold of some brownies that are supposed to be strong like this, and give them to her without her knowledge of the content. Should be good for a laugh.
OR just give her a regular brownie and TELL her theres buds in it, then make fun of her when she pretends shes sooooo rippppped.
i also found dangerTILTs suggestion hilarious