Dear Annie: My daughter has been engaged for several months. Her invitations for the small, family-only wedding were handwritten and mailed six weeks before the event.

The wedding is in two weeks. Yesterday, my sister-in-law announced that she is giving my brother a surprise party on my daughter's wedding day, three hours after the ceremony begins. It's two weeks before his actual birthday. And it's not as though she planned it because we'd have a ton of relatives in town for the wedding. There are only two family members who don't live nearby, and they are only a couple of hours away. She could have scheduled this birthday party at any time.

This is the tackiest thing I've ever heard of. I don't even know how to pretend it's OK. I am just speechless. Your thoughts? — Bride's Mother

Dear Susan: We completely agree that your sister-in-law has done something both tacky and with underlying hostility. You don't have to pretend this is OK. It is not.

Would your husband speak to his sister-in-law about the party and ask that it be rescheduled? Is there any other person who can intercede and convince your sister-in-law that this reflects poorly on her? You also can tell her how unhappy and shocked you are by her decision to plan this party in a way that deliberately takes attention away from your daughter's big day. Especially when she didn't check with you first.

If she refuses to change her plans, we recommend you ignore what you can, and accept that your sister-in-law lacks class. Do your best to minimize your disappointment and any damage to your daughter and her groom. Put on a good face and make the best of the day. Please don't let anyone ruin it.

Dear Annie: I am a psychiatrist with 35 years of experience and would like to comment on the letter from "Worried Mom." Her ex-daughter-in-law, "Mandy," had multiple affairs, eventually abandoning her family and leaving town for some man she met on the Internet. Now she is emailing family members, demanding money and threatening to sue for sole custody of the children.

In no way should the writer's family respond to Mandy's emails. She sounds like she is seriously mentally ill, and the truth is, psychiatry doesn't always work. People like "Mandy" are resistant to the meager therapies offered to people with severe pathology, and they get worse with age, as they are increasingly isolated, addicted, rejected, entrenched in their defenses, etc.

The only thing to do is nothing. There is no "rapprochement" with a deranged and desperate person. We don't like to advertise our failures, but I guarantee that most seasoned therapists would agree that people with the described pathology never get better. — Portsmouth, N.H.

Dear Portsmouth: Most children desperately wish for normal, stable parents. Even when they realize a parent is mentally ill and incapable of such normalcy, they still hope for some type of reconciliation, if only an acknowledgement that it won't get better. We appreciate your honesty about therapy's limitations.

Annie's Mailbox is written by Kathy Mitchell and Marcy Sugar, longtime editors of This Classic Annie's Mailbox column was originally published in 2015. To find out more about Classic Annie's Mailbox and read features by other Creators Syndicate writers and cartoonists, visit Creators Syndicate at www.creators.com.