Issues with Frannie Goldsmith (the Stand)

Its pretty impressive how in a story where 99% of the world's population gets wiped out by a plague, and there is an apocalyptic struggle between good and evil happening, one character could have caused so much trouble to be avoided. I mean, she basically kept it secret for how long that Harold has passed his breaking point? She breaks into his house and leaves obvious signs of a break in, and doesn't find it the least bit suspicious when Harold is studying her sneakers? And don't get me started on her random fits of giggles.