Recently, she came to visit and stayed with my fiance and me and our kids.Woah, hold on a minute there. "Our kids" as in – you made the kids together? Or "our kids" as in "my kids and his kids"? If is the former, is that why you say he is your fiancé – so that it will seem better that you are shacking up and making babies out of wedlock? Or do you actually have a ring and date? If you are "blending" kids, it is even worse. But let's get back to your complaints about your sister.
At brunch, I fed one of the kids healthy foods at his doctor’s request, and the moment I was out of sight, she loaded him up with cookies and cake from her plate.Out!
Anytime we went anywhere, she followed my fiance in stores when we were browsing. At a family event, she waited until I went to the restroom to ask my fiance how we were doing and to offer support "if he ever needed anything." I don’t understand why she seems to go out of her way to make my fiance happy by siding with him at every opportunity.Ditch your sister. But how did your fiancé handle the situation? If he handled it well, and he is the father of your children and generally husband material, go down to the courthouse or the county clerk's office and get married now, instead of continuing to shack up. Otherwise, dump him, too.
Margo pretty much agrees with the "ditch your sister" part. Check out the other letter in the same edition o the column, in which a child describes being her abusive mother's only friend. So sad.