Looking for a story where a woman voluntarily loses her intelligence

[ArchangelDiane]

I am looking for a story I believe I read on this site a while ago, in which a professional Hispanic woman reunites with an old boy friend. She ends up going through a lab experiment to dumb herself down and her sister takes part to help and dominates here. She end up losing more intelligence than planned and get turned into a servant by here sister, and her sister starts dating the mechanic and helps him move up in life.