How do I do stop my 3 month old from sucking her thumb?

My 3 month old is a thumb sucker too. When I pull her finger out of her mouth, there's a loud "pop". I bought a pacifier for her but she's too used to the breast so she refused the pacifier as well. I don't mind that she sucks her thumb because it's always there when she needs it. As for weaning, she can self wean. Babies are really smart. If you don't want her to suck her thumb, I've seen how some parents tuck their child's arms into their pants so they can't suck their thumbs. Haha!