A few days ago, she finally started signing a new sign (her first sign, unless you count waving and pointing which I guess are technically signs). She now signs "milk" very distinctively. It's clear she knows exactly what it means, since she does it as a response to a question (like "do you want to nurse?") as well as doing it while tugging at my shirt. It's a great signal to see that she's understanding and learning new words.
If you have seen how often she says "hi", you will see the only downside to her new word.