Have you ever played at thumb wrestling(One,two,three,four i declare a thumb war)?

when i was in high school i had a classmate that i always challenged to thumb wrestling but even though i was a big boy and she was a skinny and petite girl i was never able to beat her. i could never catch her but when she caught me the grip of her thumb was too strong and there was no way to get free.
a little while ago after many years i met her again and as a joke i proposed a challenge like in the old days and she gladly accepted. guess who won? her again, immediately and without the slightest effort. So i asked her let me try to get free while she keep squeezing my thumb but I couldn't move it even a millimeter as if i had no strength. Have any of you been defeated by a girl in this game? And does strength really matter or do other skills like technique, agility and thumb size matter?