Well there was a scene where Jill was at the mansion she lives at when she passes Rusty, he formed Dik shortly after that and from what I saw in the scene she had been at that mansion for a bit before Rusty turned up. Dik has only been around for three years so guessing that might mean Jill is older than she appears.The other obvious one is that Jill makes a big deal about the tree at the picnic, about how it was her and her sister's favorite spot where they would write and such. In the flashbacks to the mc's mom, she's writing under a tree, it is so not the same tree. She's allowed to write under any tree she likes, but it's just another counter argument (if the tree was the same, then that'd be a serious game changer in this argument).