We call it sleep underwear and he wears it during nap and bedtime. Is she waking up dry? If so, maybe she is ready for regular underwear. You can get a thicker absorbency and maybe something to protect her mattress..
I haven’t personally been through this but a friend of mine had this issue. She used the disposable bed pads under the sheet. Yes it still makes a mess if she happens to have an accident but it wouldn’t soak through to mattress. May be an option if she is waking up dry most of the time
We’ve been using pull ups at night instead of a diaper! But we call it “nighttime underwear” instead 😂 he had no issues with it since it was something new and wasn’t the same as a diaper!