Am I wrong in this situation?

So, my sister, my daughter, and are at the house relaxing and being lazy. My daughter was snacking on a bowl of dry cereal. I left the room for maybe 10 minutes. I could here my sister laughing from the other room. When I came back, cereal was everywhere. I mentioned to my sister that since she was the one that let her throw cereal everywhere then she was going to be the one to clean it up.

She ended up cleaning it up even after she swore she wouldn't. She put all the cereal back in the bowl and gave it back to my daughter. My daughter swiftly dumped the cereal back onto the bed. I was irritated with my sister for letting her make a mess, and she was irritated with me because I also could have stopped her. I did not see what she had done until after she did it. My sister had just finished playing with her and watched her do it.

I this all sounds petty, but this is just one of many instances of, "I let her make the mess, but now you have to clean it." I'd come home from work and they'd start telling me to clean up something she had knocked over or had thrown around. It's extremely annoying.

So now I ask, am I responsible for any messes made when she's not under my supervision? Am I wrong for being annoyed?