R.M.
I don't think I would make too big a deal out of it. Maybe she didn't really take the food to her room because she was hungry...maybe she just did it on a whim and when you questioned her about it, the logical thing for her to tell you was that she was hungry.
My stepson used to hide food...but not because he wanted to eat it later...much the opposite...if he didn't like something that he was supposed to eat for lunch or dinner he would secrete it in pockets, etc...then go hide it in his bedroom...lol.
The cookies that she took...that the two of you had made together might have just been really important to her...since the two of you had worked on them together!!
Personally I wouldnt make too big a deal out of this....it is probably just a passing phase