I was the thumb sucker, complete with twirling my hair. Nobody at home did anything to get me to stop. They ignored it completely because really - what can they do? I was quite aware it was not appropriate at school, and eventually I switched myself to biting on pencils, pens, chewing on the inside of my mouth (cheeks), my hair (when it was long enough) and sort of sucking on the skin over one finger - hey - at least it wasn't my thumb.
Oh - and chewing gum. I was the kid teachers allowed (encouraged?) to chew gum in class. Now when I teach... yes... there is sometimes a child I also allow to chew gum in class!
As for stopping at night - that came even later.
Did I need braces? YES. But so did one of my brothers, and he never sucked his thumb, nor did he use a paci.
And no - I didn't suck my thumb in highschool (ha ha - at least not in public!).
By the way, I have no idea what your daughter deals with in life. I was very very stressed - physically with a legs/back problem and lots of allergies, AND I was stressed emotionally as well. Few kids I know suck thumbs in class at 7 or 8 years old, but the ones I know also are stressed. Of COURSE, that does NOT mean that is the case with your daughter - I have a VERY small pool of children I know (myself included).