My naturapath said that most bugs are food-related in that they either come directly from food or from food prepared by someone who touched a surface which had the (please excuse - yuck) bacteria form either the vomit or diarhhea. This can happen quite easily when the toilet is flushed w/o lid down and the particles go 'everywhere" according to her. She said casual contact with someone is rare to infect another. Your case however, seems like you entered the pit of sickness and picked it up. Even if she cleaned, it's hard to get it all I think.
Have you tired Nux vomica homeopathic? there are other homeopathics for vomiting too but I think nux is one of the maintays. Check with a book or with your naturopath.
Gosh, good luck. I hope your dd is feeling better.