DEAR MISS MANNERS: My brother’s wife absolutely hates his ex-girlfriend and verbally states so at every given opportunity. She does so using vulgar terms, regardless of who is around — my children, my parents, other family members, complete strangers.

This now-married couple began their relationship while they were both in other live-in relationships. They would lie to their partners about where they were and who they were with. My brother kept it secret from our family for years while they cheated together, and when it all came out, there were messy breakups.

The two of them have now been married about two years. They have a lot of trust issues with one another, and they do not have a peaceful marriage.

We all got along very well with my brother’s ex-girlfriend, and I still value her friendship. My brother’s wife told me to tell my mom that if we do “anything nice” for the ex-girlfriend that it would be showing her disrespect, and that she is “putting us on notice.” The ex-girlfriend, who is now happily married and expecting her first child, remains a dear friend. She is kind and loving, and has done no wrong in all of this.

My brother has often asked me what I think of his wife, and, Miss Manners, I am at a loss as to how to respond. I have told him, “I don’t know her well enough to answer that yet.”

How do I shut down the ultimatums and let my brother’s wife know that I do not wish to fight with her? How do I politely tell my brother what I think without hurting him or pushing him away? He is asking what I think of her so often that I don’t think he believes my line anymore.

GENTLE READER: Although she does not know your brother, Miss Manners agrees that he does not believe your feelings for your sister-in-law are neutral. This is not a problem, but an opportunity, as your sister-in-law is clearly not someone with whom you can have a civil conversation about the ex-girlfriend.

The answer to your brother is that you really want to love your sister-in-law as you know he does, “but her ultimatums about the ex make it a challenge.” This may be more subtle than the quid pro quos to which your brother has become accustomed, but for that reason, it is less likely to damage your relationship with him.

DEAR MISS MANNERS: When, if ever, is it appropriate to use “reply all” in group emails? Only when asked to? I find it annoying when people reply to all.

GENTLE READER: The proper time to reply to everyone is when the answer can reasonably be expected to be of interest to the group — and when your response respects the context, tone and subject of the original.

A company email from the boss explaining a new policy is not an invitation to tell everyone you object. A serious email about the water being shut down in the building is not an invitation to make a joke about the cleanliness of said water. And an email from your cousin announcing the date for the family reunion is not an invitation to open a debate about who is hosting Easter.

Please send your questions to Miss Manners at her website, www.missmanners.com; to her email, dearmissmanners@gmail.com; or through postal mail to Miss Manners, Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO 64106.