oh i know they are already worthless and contain absolutely nothing
But it would be funny to replace them with an indistinguishable placebo, then reveal all to her down the line
( applehead herp derp, Sun 17 May 2009, 19:08, archived)

It would be better for both of you if you explained to her how medicine worked.

( WormuIus, Sun 17 May 2009, 19:15, archived)

Sister: "I had a stomach ache, and was feeling fatigued and took such and such a homeopathic remedy and felt much better afterwards. Ergo it works"
Me: "No you didn't. I replaced your such and such homeopathic remedy with pure sugar pills a week ago. What you took was a placebo. Ergo homeopathy doesn't work"

Sister: "Oh. What a fool i've been. Thanks for enlightening me with this marvellous ruse"
( applehead herp derp, Sun 17 May 2009, 19:18, archived)

If she really believed in homeopathy she could argue that by redcing the chance of an active ingredient you have actually made the medicine stronger ;)

( WormuIus, Sun 17 May 2009, 19:20, archived)