Hi A....if you're child is 22 months old, maybe she's trying to tell you something--She's Tired Of That Pamper! My daughter did the same thing and it drove me crazy!! I told a co-worker and she said, "Stop making her wear the diaper if she doesn't want to." This lady has 4 sons so I totally trusted her advice. She told me to put 2 sets of sheets on the crib and place a couple of thick towels on top for my daughter to sleep on, make sure my daughter pottied before bed, and then put on a pair of underwear to sleep in. Dora panties worked best for her because she didn't want to "pee" on Dora. Now, this isn't a fairytale, so she did wet the bed a couple of times. Since I work, I don't have a lot of time in the mornings for clean up. I simply took the thick towels and the first set of sheets off of the bed and threw them in the washer while the 2nd set remained dry and stayed on the bed.
I did the onesie thing too but that was when my daughter was younger by 22 months, most girls that I know are either trained or starting to train. She's probably just growing up and not wanting the diaper anymore. My daughter's old sitter used to say, "You've just got to trust her." I think you just need to trust that she's ready and go with it.