You could probably watch the baby as it took a nap and she could use that time to clean up after herself. You aren't her slave and it's just plain rude for her not to have the decency to clean after herself. You should talk to your husband, too, so he knows that HE needs to clean up after himself. I am sure they are both at fault in this as you have kept the space you're in fairly clean. I think both of them just expect you to clean after them so they are surprised there is a mess in the house because no one is behind them cleaning after them.

Talk to them and set up some system to get them in shape.

My mom actually trained my dad to clean. He cleans the same things around the same time everyday so things are rarely messy at my parents home. Another thing my mom ingrained was to replace everything you've used. (Which I've finally started to get OUT of the home!) So if you have dirty clothes, they should always go in the hamper...or if you dirty a dish, wash it immediately after use. Don't leave anything in the sink...etc