The hospital must have a proper complaints procedure for contractors and sub contractors. My first port of call would be the person who you originally dealt with and ask them about your concerns about the woman and about the complaints which in terms of her job, who her father is, and the job you do, could be a conflict of interest.
It may be worth pointing out to the person in authority, or the person who you dealt with to get the contract, that the woman concerned has a father who runs another w/c company, who may (or may not be) sniffing around, and that may be why there are complaints.
Sometimes speaking to the right person in these situations can squash a problem before it takes a foot hold.
It also might be that the complaints have nothing to do with the woman what so ever.