B.S.
Oh goodness, forget what those books say. I think its quite normal for a 6 month old to wake up once or twice a night. I know many babies (my own included) who did not sleep completely through the night until they were more than a year. If your baby cries, nurse her or give her a bottle quietly and quickly (or if she's really not hungry, just snuggle her a bit and give her a comfort object like a pacifier or blankie). Then settle her back in for sleep and go back to sleep yourself. I would put the emphasis on getting you and baby back to sleep as quickly as possible. Do whatever you can to accomplish that. I do think a six month old should be sleeping for a good 12+ hours at night, but that doesn't mean they don't wake up briefly during those hours for some milk.
Good luck!
B.