HELP! I am on day 51 with almost daily going to the clothes shop and still no skirts. Each day I go in, I usualy buy either 1,2, or all of her clothes. Am I missing something? I know DEVs said that it's random, but is it 100% luck based? Would be great if after a couple times of not buying anything, you could tell her what kind of clothes you're interested in.

It's luck based, but some items have more conditions. Don't remember the exact conditions for skirts, but your best bet is to talk with the bot more.