Her best revenge would be to take their ‘artworks’ and sell them on ebay for like $3 each, to several friends on condition that they sell them in a chain to each other for no more than $5, accepting no other bids.
Then put up faux sales ads, with those pictures marked as “sold”, again for a pittance. Again do this several times. This would drive the market value of their other ‘works’ into the toilet.
The art market is downright vicious this way, and could ruin the careers of many of these “artists”.
I like that idea :)