well you can try limiting what they can see of all of your posts by adding them to a restricted list which only allows them to see your totally public posts and any post where you have tagged them...although point one is that I think this is overridden of a mutual friend tags you both in a post.....the other thing I am not sure about is what happens if you are both in the same selling group....of course you can block them but I am assuming you don't want to do that?