From my memory of the novels the handsome was more in reference to her youth, and "crone" is the word most frequently implied in her direction at the current timeline, and you don't usually find good-looking crones. It also depends which book you're talking about.
Either way, your interpretation of the book and mine may differ. For me part of the appeal of Granny Weatherwax is that she is an atypical heroine and attractiveness or unattractiveness is part of that distinction. For you this may be different, and that is your choice.