Wow, that's difficult! I have to say that I see women posting on here all the time about needing someone to care for their kid. This isn't too different from a newspaper. I don't know any of the people on here personally and being in the internet business for the past 13 years, I wouldn't trust anyone site unseen to know exactly where I live and especially to take care of my child.
That being said, it's just an advertisement. I'm sure he would interview the person and get background information on the individual before allowing them to watch his children. If she does not believe this is the case, then she needs to speak up and require that they chose someone together or she needs to talk to her lawyer about this process. It all depends on their relationship. I would highly suggest that she talk to him first and to try to maintain good relations with someone that she will have to deal with for the rest of her life.
I don't know how old her children are and it does make a difference. If her children are not of an age which they understand their own boundaries and the limits to which a person should be able to speak to them or touch them, then she needs to be the person to make the arrangements for the care of her children. If they are of an age which they can voice their issues, she needs to ensure her children are well advised on their personal boundaries and that they can ALWAYS tell Momma, no matter what. This is a scary world we live in!!!
I am so sorry that your friend is going through this! I hope it gets resolved to her satisfaction!
Jodi