DEAR MISS MANNERS: I have a family member with whom I have a challenging relationship. I go out of my way to be civil and polite, but also to keep my distance. (Avoiding her completely would mean declining all family gatherings.) She singles me out for catty behavior, and is outrageous, but not insulting, to others. This dynamic has been going on for decades, and I am under considerable pressure from the rest of the family to ignore it and not rock the boat. One of her standard jabs is to bring me a gift with an insult attached. Due to a health issue, I was unable to work out for several month…