Dear Abby: My sister-in-law “Bethany” has been diagnosed with PTSD from her military service. For the past 15 years, Bethany has picked fights with my wife, her sister, over anything and everything. She feels my wife “changed” after she married me.

Bethany didn’t like how we treated their father after we moved in four years ago so we could take care of him. (He recently passed.) She also doesn’t like that we are living in the house that was her childhood home. She starts fights that escalate into screaming matches, while making herself out as the victim. She keeps reminding us that she has PTSD. My wife screams, cries and sobs during these conversations.

My wife won’t cut Bethany off because they’re siblings, but I’m sick and tired of seeing her in tears trying to figure out what she did wrong. Whenever Bethany comes to visit, she ends up staying at our house. The fights are unbearable. I have begged and pleaded for my wife to cut her off. It’s affecting me now. Any advice would be appreciated. — Powerless in Michigan

Dear Powerless: Please share this with your wife. Has it not occurred to her that she has done NOTHING wrong, and that Bethany’s rages may have less to do with PTSD than plain old jealousy? By now, the two of you must have realized that the price of having a relationship with her sister is too high. That your wife would allow herself to be repeatedly abused this way mystifies me.

When Bethany starts up again, your wife should hang up the phone. If Bethany shows up and can’t control herself, she should not be allowed in. If she’s already in, she should be told to leave immediately. Until the two of you draw a firm line, nothing will change, and it could very well destroy your marriage.

Dear Abby: After 28 years, I found out my husband, “Jerry,” was having an affair. While we were in the middle of the divorce, my nephew was getting married, and I told Jerry that, considering the circumstances, it was improper for him to go. I also told him that although he was denying everything and telling our daughters he had done nothing, my family knew everything.

Jerry insisted on going, but I told him he would NOT be in family pictures and wasn’t invited to the reception. Abby, he insisted on sitting in the pew with our daughters and me, and even tried to walk my mother in. Was what he did in bad taste and improper etiquette? To me, it felt like another slap in the face. — Divorced But Not Done

Dear Divorced: That your almost-ex-husband would force his way into the wedding and sit with you and your daughters was gross bad manners. Was he invited by your nephew’s family? If he wasn’t, I hope he didn’t show up uninvited to the reception, which could have caused a major disruption. I think you will be well rid of this man.

Dear Abby is written by Abigail Van Buren, also known as Jeanne Phillips, and was founded by her mother, Pauline Phillips. Contact Dear Abby at www.DearAbby.com or P.O. Box 69440, Los Angeles, CA 90069.