Re: me , my mom and my wife
How long will your parents be living with you and your wife? Is this a short-term, just a couple months situation, or is this a really long term, open ended situation? If this is long term, how well do you think your wife understood the situation before your folks moved in? Did she know your parents well enough to know what she'll have to put up with, or was it more like: Well, these are ran1976's parents, I'm sure they'll be saints and I won't even know they're here? Do your parents have cultural expectations of a daughter-in-law that your wife does not share, and are those expectations creating more tension?
1. Get your parents a cell phone. Make it clear that they are to use this and not the home phone. Make sure it is a good plan for international as you will be paying for this, or has a hard cut-off after so many minutes of international calling. This will give your mother the privacy she expects: she can walk down to the park and make her calls. When my in-laws were living with my husband's brother, they would do just that: walk down to the park, call my husband, and complain about his brother's wife. Did she know they didn't like her? Sure: she doesn't get along with any of the family, and someone who enjoys criticizing others that much has to know she's unpopular. But she didn't have to listen to them, and that helped keep the peace.
2. If your wife had walked into the room, or picked up the home phone to use it inadvertently, rather than deliberately, how would you feel about this situation and how would you handle it? Are you sure that your wife picked up the phone to listen to your mother and sister, or did she pick it up to place a call and discover your mother was using it? Yes, your wife is in the wrong to listen in to a private conversation, but your mother made a poor choice to complain in a situation where she had no reasonable expectation of total privacy. An apology from both sides would be appropriate.
3. If this is an open-ended visit--your parents have immigrated--look into what it will take to get them into their own place. This may be the only way to restore peace. Maybe remodeling your basement into an in-law apartment will suffice, maybe you need to rent them a tiny studio apartment. Involve your wife in the process so, if it ends up being impossible at least right now, she knows you're trying.