My 3 month's daughter is sucking her thumb all the time. What should I do?

Hi, You can perhaps give her a pacifier to distract her. Since, she is very small, she would not understand even if you keep taking her hand out of mouth. And you cannot be around her 24/7 doing that. For sometime give her the pacifier and then wean it off, by that time, hope she forgets putting her thumb in mouth. :)