Professor Trelawney can actually predict things.

I do.

When you think about it, she actually DOES predict what happens.

For instance...Book 3

She predicts that;

What Lavender Brown is dreading will happen on October 16 IT DOES!!!
"Near Easter, One of us will leave us forever" - That was Hermione
She told Neville that one he had broken his first teacup, get a blue on, that happened
She says he will be late to calss next time, so he will need to catch up - He is
And then of coursde there was the one about Wormtail.

See? She CAN predict things. Just not under pressure. And she does get SOME things wrong.