My 16 year old friend still sucks her thumb
I have been friends with this girl since the 8th grade, however my first encounter with her was in the 7th. Someone pointed me out to her as "the girl who sucks her thumb". I thought this was weird, and must admit that I still do as she is now 16 and still does it. For instance, sometimes when we are in class copying down notes she just starts sucking her thumb.
Is this normal, because I feel that it is not, but maybe I'm just narrow-minded. Is it more common than I think?