"想不通"怎么翻译好?

I don't understand...

太难 or 心里委屈

我想不通她看上他什麽了。:
I can't think what she sees in him.
我真想不通你为什麽让孩子一个人走。:
I cannot conceive why you allow the child to go alone.
我想不通你怎么会让孩子独自去旅行。:
I can't conceive of your allowing the child to travel alone
我怎么也想不通你居然丢失了这样一根珍贵的项链。:
I'll never get over the fact(that) you manage to lose such a precious necklace.

心里委屈想不通I can't get through.

I just can't figure it out

I can't accept it .

I can't understand and even hard to accept.