No thumbs!

OMG my daughter is going to be the death of me! I am SO against thumb sucking. I mean yeah- it's cute when they are 3 months old. It ISN'T cute when they are 2,3,4,5 you get my point. Well, my little Miss Thing has started putting her thumb in her mouth. I know I need to squash this behavior early so she doesn't start a nasty habit but how do you do that with a 3 month old baby? When she sticks it in there I pull it out and tell her "no thumbs" --- like she can understand me! :) But right back in it goes. Ugh... I don't know what do to. I know many people feel differently than I do about thumb sucking and I am not intending to judge your parenting. If it's ok with you it's no skin off of my teeth but I am against it for my children. Max seems to have no interest in his thumbs. Now the rest of his hand is a different story. He can practically get his whole fist in his mouth!

Any advise on how to stop this? Is she too young to put that nasty tasting stuff on her thumb. I need to find a way to discourage this! :)