He did have a point, their parents and siblings had no idea of Loras' preference, of that Margaery was very sure. And the one time they may have found out she had taken care of, though Loras would hopefully never find out about that.
Margaery nodded, "Okay" she agreed, "But if you can't just try to make sure they do not involve you"
Being disinherited and cut off wasn't a big worry for her, she had more than enough money to support them both, what concerned Margaery was Loras losing contact with the rest of the family. They may not be close but it wasn't fair to him to be forced into that situation.