Confusion with Words

Last weekend while visiting my brother and his family, my girls slept on a pull out sofa for 2 nights. After the first night K came up to me the following afternoon and said to me, "Mommy, my sheets last night were greasy."
"What!?," I asked. I was very confused because my sister in law is one of those "Super Moms" and always keeps a clean house.
"Greasy?" I continued.
K thinks long and hard and says, "No. I mean it was kind of crusty."
"CRUSTY??" I am still bewildered that she would refer to her sheets as greasy or crusty.
K thinks about it some more, knowing that she is just not saying the right word, and she finally comes up with, "No, It was sandy."
"Oh," I replied. This makes more sense to me, but still, SANDY?? In North Carolina? In the Mountains? No where near any sand?

That evening while crawling back into the sheets for her final night sleep there, we discovered that the sheets were actually CRUMBY...not greasy, not crusty, not really sandy. I am thinking that her older sister snuck some cookies in the bed the night before!