So it seems that something I was waiting to happen finally did.
Léa has picked up no.
Surprisingly, so far she's used it very sparsely and (not so surprisingly) in context.
The other day, she was being very obnoxious and kept going on the couch even though I did not want her to and kept taking her off - it seemed a game for her but I didn't enjoy it. Eventually, my "get off" got said probably in a very fed up voice and when I got up to move her, she said "NO!" (or at least it really sounded like NO!) - but given it had only happened once at that time, I thought it might have been a fluke.
However, this morning she also told no to the Boy - she was on the bed and he wanted to move her so when he went to pick her up, she ran away saying "NO!"
As for other noises, her favorite random noise is still the phone dialing/ringing but lately she's also been very keen on doing raspberry noises and it's slowly coming up to rival phone noises!