Dear Diana,

I am 32 and have been involved with a 26 year-old woman whose marriage has been pretty bad. We have grown closeu00a0 and she tells me she wants to be in an "open relationship" with me. We have only been physical a few times and I'm okay with the fact that she wants to sleep with other men, because I knew this was going on. But now, she has asked my permission to have "meaningless sex" with my brother.

I tried to explain to her how that would hurt me and that I was fine with her wanting other men, but family was off limits. How do I get through to her on this? We care for each other but she says that me saying no has hurt her. I just feel she doesn't understand where I'm coming from. Would appreciate any insights on this subject.

Name withheld