What Elish did to her was quite simple.
First, he told her a tragic little tale of her town's invasion and how it was actually in the notice of the gods. After all, nothing happens without their knowledge, at least according to the humans.
They watched her struggle and suffer as well as the other children but refused to help.
Just as they watched countless humans and people suffer without helping.
"If the gods are omnipotent and love you all, why aren't they helping? Why can't they make everyone happy?"
By planting that little doubt in her mind, her faith slowly and assuredly crumbled. After that, it only took a little bit more.
The apostles, by painting them as people used by the gods and puppets who also used her, she didn't want to be that person anymore.
Being used by selfish gods who sit back and watch as everyone suffers without a care. Perhaps they even enjoyed witnessing such tragedy.