socially taboo? yup.
chances are she's always held her dad's hand since she was little and views it as a bond she shares with her dad.
i comment this way due to something i noticed from my son. each night they come to us for goodnight hugs and kisses. our oldest son always gives a peck on the lips.
now i was raised that kissing on the lips had a romantic component and for family we'd kiss on the cheek.
i was a bit perplexed on how to handle it so i talked to my wife and she said that it really wasn't a big deal and he may grow out of it. in the short term, it is just routine.
chances are, if someone has something going on with their daughter, they aren't going to publically display it. as someone said, malice is in the eye of the beholder. i see it as a woman doing something she has been doing since she was a child, and a father that may be aware of the social taboos, but doesn't want to break his little girl's heart by changing a routine for the sake of others