I feel you should trust your instincts here. If it were me I would go straight in with, "if you need help I can call someone for you" or allow her to use the salon phone (if cordless) to call someone she trusts if she is in danger or needs help. If this man is abusing her and you ask her if she's OK she'll just reply with "fine." Do your homework, get the numbers of local refuges or hostels, mental health support, womens' refuge etc and have them all ready before you ask is she needs help to be safe/free. This man may not be her father, she could be a slave, this is becoming more and more prevalent in the UK, we know have several charities that deal with human trafficking. If you need advice call one of these charities first, they may be able to talk you through the signs you are picking up on and advise you how to move forward. Good luck and well done for spotting this.