could trigger the shrink by having your sis randomly ask you to go to the supermarket. Since you're slightly shorter, you can try to get the item, which is out of your reach. When you can't, the nanobots insist you find help, someone big and strong to help you. Maybe they could "help" you too
if you refuse, you get shrunk and a nice man helps you making you feel even smaller
Could also tie into any storylines you want to advance investigating the mental changes. (which could make conversations with Eve interesting, as you're in her model. She chose submissive. (Potentially seeing you submissive makes eve awaken to dominance?))