I was eating salad with avocado when Bella flew to my shoulder. She wanted me to pet her, and I did, but then she didn't like something and rapidly moved her head, basically "kissing" me in my mouth with her beak. I am afraid she could receive some avocado residue. Should she be OK?
I heard that human saliva (even without avocado can be poisonous to them. Is this true?

Human saliva contains bacteria that's not great for birds, but the chance of them actually getting an infection from it is pretty low.

Avocado can be toxic to some birds, but there's a lot of variation. The problem comes from a chemical called persin in the avocado. Some animals are sensitive to it and some (including humans) are not. Some avocados have more of it than others, and some birds are more sensitive to it than others. I don't think Bella could have gotten enough avocado from a quick "kiss" to do any harm. The problem comes when a sensitive bird eats a fairly large amount of avocado.

So it's most likely that everything will be fine. Certain types of softbills aren't bothered by avocado at all, and it's common for the owner to give them avocado as a normal part of their diet. But at least some parrots do seem to be sensitive to it. We don't really know very much about how dangerous avocado is for parrots, so it's best to avoid it.

thanks Carolyn. She is fine!

My bird tries to get food out of my mouth all the time... He seems to think that what's in my mouth is better than what's in his dish.

Same here LOL

Well, the grass is always greener on the other side of the fence (or of the mouth)...