Open minded is indeed a matter of opinion. Going to mean different things to different people.
Open minded strictly speaking just means you are willing to discuss anything. It does not mean you are willing to do anything and everything. It does not mean whatever you want. I understand why the ladies get tired of some of us guys. In the context of what the op posted the girl has clearly listed her no list and it is clear that open minded just means she provides services that are illegal to openly advertise but you know what she means. Sorry, do not know the girl in the ad but do not feel she is misleading you in any way.