S.S.
I was a finger sucker until I had to go on a camping trip with my school classmates and there was no way they were going to see me doing that and that was the end. My son was a thumb sucker until he was 8, but only when he was very tired or concentrating very hard. Picture a very cute little 2nd grader at Short Stop sucking his thumb. It allowed him to focus. A lot of my friends kids quit on their own by 1st or 2nd grade. There will be parents like me who just let it run it's natural course, but then you get all the nosy Mrs. Kravitz's telling you you're kid is too old to suck their finger/thumb while their 4 yo is running around with a binky and a bottle. And there will be parents/dentists that will tell you it's really bad for their teeth/mouth development, but try reasoning that with a 2 or 3 year old. If you really want her to stop you might try setting a date so that she becomes a "big" girl, like her 3rd birthday and that she can stop on that day. **shrug** I have also heard about taping oven mitts on their little hands. My son would have made me more miserable than him on that. This is a challenge and personally, with all the other challenges my son presented me with, sucking his thumb was the least of my worries. Just know that very few college freshmen suck their fingers/thumbs so they will stop naturally on their own (except for that one woman who was in her 30s and was on Dr. Phil, sucking her thumb while she was doing computer programming---YIKES!)
S.