Hi Mondelo66: You sound rather miserable, trying to deal with your SIL. Hopefully some of the techniques mentioned below can be helpful.
Sister in law invalidates me and terrible listener
On this website, when "validate/invalidate" is discussed, it's in regard to feelings, not agreement/disagreement. Are you talking about feelings or agreement with facts or opinions?
In the context of "feelings", it's important to NOT invalidate by word, expression or body language. So, you can just NOT comment (don't invalidate feelings), or you can acknowledge their feelings i.e. "You sound angry", "I'm sorry you are upset. I need to let you go & we can talk another time".
Never agree with or validate facts that aren't valid.
You can't change your SIL, but you can change how you interact with her and react to her. Some things to start with:BOUNDARIES: Set your personal boundaries and enforce them. You can't expect anyone to just honor your personal boundaries. They are yours and you have to consistently enforce them. If once you decide on a boundary, if you aren't consistent in enforcement, then it won't likely work for you.
DON'T JADE: Don't argue with SIL. Don't Justify, Argue, Defend or Explain (JADE). Change the conversation or get out of the discussion as politely as you can. Visit the restroom, get off the phone, get some water, etc.
GREY ROCK: Stay boring and neutral. Don't offer information about you or share personal details about your family. Be pleasant. Don't take a position of anything that could lead to JADEing (Justifying, Arguing, Defending or Explaining).
BIFF TECHNIQUE: Be Brief, Informative, Friendly & Firm. This can be a good technique to use with emails and texts. It can work verbally, as well.
The above 4 strategies are good to help prevent problems and keep you out of the drama. SIL probably won't like it, if she is someone who wants all the gossip & details about everything. It's up to you to maintain your boundaries and NOT feed her need for drama and control.
A couple of extra tools to try during conversations:
PRACTICE USING "SET": SET statements contain: Support, Empathy + Truth. This can take some practice & is probably something you might try writing out a few times.
USE "I-STATEMENTS": An "I-Statement" takes the "you" out (as in SIL) and puts the "I" focus on things (you): i.e.:
I feel ________ when __________because _________. What I want is ________
SAMPLE: I feel frustrated, when I'm not listened to, because the conversation becomes one sided. What I want is to have a mutually respectful conversation, where I am given an opportunity to be heard.
If you to to the large green band, at the top of this page, you will find a "Tools" menu. You will find links there to lessons on "Boundaries", "Don't Invalidate" and to "Workshops", where you will find a lesson on SET, as well as several pages of other helpful strategies.
Pick one or two strategies and start using them. Take it a step at a time. I think that you will find that once you change your strategies with SIL and quit expecting her to change, that things will get better for you.
Some people like to give specific examples of an interaction. That might be something you want to do.
What strategy mentioned above, might you try using first?