@DollDream
That's actually the first thing she tried to do in chapter 3.
But Klaus used a maze spell to make it impossible for the adult to stop him from exploring the ruins, so she wasn't able to get to them.
That's why she decided to enter the ruins herself.
As for why she doesn't ask Klaus to undo the spell now the she has find him?
I guess she is worried that, by the time the adults arrive, it will be too late for Ann.