Hmm I don't think that's true at all. Can't speak much for Annie, but Bert did say the only time they had some respite was while they pretended to be soldiers, and that they truly saw the rest as friends. As for Reiner, he mockingly made some observations as to how they truly were devils by saying they would share a half a potato but not really doing so... They all saw for themselves that the stuff they were fed since birth was lies, but they still had a mission to carry out and come back home to their families. Gabbi will surely remember what Reiner said and will probably connect the dots. I mean personally I much prefer for Gabbi to see the truth by herself and without the aid of any of the main cast, I think that's a clever way to go about it. Now, will she change her whole mind right away? Probably not, but it may very well be enough to plant the seeds of doubt in her.