Toward the end of Frozen II we learn that the voice that has been called Elsa into the wilderness, and eventually to Ahtohallan is actually
Iduna is aware there is an element of risk with this journey, but obviously she doesn't intend to lure her daughter to her destruction. She has justified confidence in her daughter and means for it to be a positive and empowering experience. And that is what happens, until at the last moment it goes very wrong for Elsa.
It seems that learning the truth about her past was too much for her at that point in time. But was there an awareness of what Elsa would find there and what might happen?