I remember a YA book that involved a family who's babysitter/nanny was implied to be magical, and as I recall she was heavily associated with lady bugs. But I can't remember what the name of the books were.
I can recall some of the cover art, where said babysitter/nanny is helping one of her kids get ready for what might have been a date or a dance. The babysitter is kneeling down as she's helping the girl with her dress, but it looked as if the girl was either floating in the air or there was electricity going through her. Also, I believe the nanny had red hair which I think stood up. The other kids were looking in from the doorway as this was going on.