L.A.
Wow, what a mess.
Really as has been said below.. There is nothing you can do about his.
You can sit her down and tell her your concerns, but this does not mean she has to listen to you or do what you suggest.
She obviously has low self esteem. The only way to get past that is through therapy so she can figure out why she feels like she has to pay for a guy to like her.
Really sad that her daughter is going to learn from her mother, to not stand up for herself.
That is what I would mention.. "Why do you think you are ok, with the treatment he gives you? Would you want your daughter to EVER be treated this way? What would you suggest she do if she ever ended up in this situation?"
then tell h er, "she is just as deserving of being respected an appreciated as her daughter does." Hope she wakes up and kicks him out of her life.