andy c
velcro! sounds like she may be about ready for a bed.

jingles
On the underside of the sheet sew two pieces of elastic on each short end from one side of the sheet to the other. This should make the sheet harder for her to take off and since they will end up under the mattress, she shouldn't be able to get tangled up in them.

Heather M
try some sheet suspenders- you clamp them onto each corner and clamp it to the opposite corner it looks like an x when you get them on the sheet . the website I found them on is www.sitincomfort.com . But i am sure that you can find them elsewhere. I hope this helps

tanglewoodlinden
Does she have a teddy or favourite blanket? She may be doing this as she then loves to curl up into the sheet once she's pulled it off. Consider placing an extra little sheet in the crib, or double sheet the mattress. She pulls the first one off and the extra is still there for her to sleep on. Alot of kids have a little comfort rug or teddy that they love falling asleep with.

Inamama
I always buy fitted sheets.My daughter keeps rolling all night and that's the best solution for us and I think for you. Try it!

KAT
I only baby-sit an 18 month old but it works when i slap his hand lightly and say no. but if your daughter still won't stop try putting her in the corner with her blanket for a certain amount of time. If she throws her blanket or gets out of the corner add on more time.

EC Expert
They make elastic straps for just this thing.You can usually find them at Linens and Things and Bed Bath and Beyond or stores like that. If you cannot find them make them yourself and attach them with Velcro. Another possibility is to put a second sheet on the bottom side of the mattress so that the sides overlap. That might make it harder for her to get it off, If your sheets are older they may not be designed to fit the newer,thicker mattresses. Maybe she is ready for a bed with a rail.