Darth Caedus
Formerly Congerking
That occurred in the 6th book. Trelawney herself is only in the 7th book briefly, in the final battle. There, she throws crystal balls onto Death Eaters from above, knocking out Fenrir Greyback.
Yep and I think it would be rather stupid to have her come back JUST for that. I think they are going to blend elements from the 6th book and the 7th book together (relating to the prophecy)