I went through the same thing with my daughter, who sucked her thumb until she was about 3, but I wanted her to stop WAY before she wanted to stop. I started telling her several things that began the decline of her thumbsucking, like her teeth were getting messed up; there are a lot of germies on her hand that could make her sick, people make fun, etc. It suonds like you have successfully gotten her to stop while she was awake, its just the sleeping thumbsucking thats a problem now. But, like your little one, as soon as she fell asleep, her thumb would pop right in her mouth. Like you, I did NOT want to put anything yucky or spicy on her thumb, so when it was time for her to go to sleep, I put a glove on the thumbsucking hand. Its non-toxic and will definitely be unsatisfying to put a fuzzy glove in her mouth. Being that she doesn't want to suck her thumb, you shouldn't have a problem with her taking it off while she's asleep. If it becomes a problem, you can do what I did initially, which was get a long tube sock and put it on her arm, all the way up to her shoulder. That way, even when she is asleep, it deters them from being able to take it off. Even if they get it part of the way off, it's long enough to still cover their hand. It didn't take very long at all for her to break the thumbsucking while sleeping habit, maybe 2 weeks, at most. If she still gets the glove off while she's asleep, you can sew a glove or a sock onto a long sleeved pajama shirt, or even just a regular long sleeved shirt. You could also safety pin it on, which is what we did initially before I sewed the glove on, but you run the risk of the safety pin coming undone, so its best to sew it on if possible. I hope this is helpful. Good luck!