When is a lie not a lie? Wondering.

I am a Christian.
Mom actually led me to a saving knowledge of Jesus Christ when I was eight years old.  I remember it clearly and fully understood the decision I was making.  I was taught right from wrong.  I was taught the ten commandments.  I was taught the infallibility of God's word.  I've built my life on these truths and raised my children by the same standards.

The last time I visited with Mom she became very angry, which is not unusual for her these days.  Mom has always had "spunk", but the dementia seems to have heightened this tendency while at the same time dulling her behavior filter.  Now when she is angered it's not terribly unusual for her to say cruel, profane things, and at times to even hit at whoever has offended her - which has always been a family member thus far.  That said, Mom is not wild.  She knows when she can act like this and when she can't.  She became angry with the judge at times when we were in court.  She spoke directly to the judge at appropriate times, stating her opinions clearly, but never once raised her voice or spoke in a manner that was disrespectful.  She totally knew what was acceptable and "behaved" accordingly.  When our case was adjourned Mom became irate with our family members.  She spewed profanity and told us over and over that she hoped we died before she did.  She accused us of terrible things and approached a stranger in the hallway telling her how awful her family was.  The poor stranger sat in silence as Mom ranted.  It was obvious to anyone near that something was not right.

I tried to calm her.
"You don't mean that Mom, don't say those things."
"You know that's not true", etc. etc.
The more I tried to calm her the more irate she became.

I've been doing a lot of reading lately.
I'm trying to educate myself and learn techniques of dealing with this type of behavior.  The first thing I learned was that I've been doing it all wrong, and saying all the wrong things.

I've read from various sources and they each advise to never scold, and certainly to never tell someone with dementia that they don't mean what they are saying.  They tell me that people with dementia do certainly mean what they say, even if it's not based in reality, it is their real feelings based on how they are perceiving the world at the moment.  The best method is to sympathize and validate their words, then calmly redirect to another subject if possible. . .Soooo, what I should have said was more along the lines of, "I know we've made you angry. . .Now, would you like some pie?"  OK, I'm being silly, but you get the idea.  I'm such a beginner at this.  I'm learning but have not yet had the opportunity to use my new found knowledge.  We'll see.  Honestly, it seems to me if the person with dementia knows when and how to behave but chooses not to adhere to this, then a gentle bit of scolding would be acceptable.  I would think, "Stop hitting.  You know that's not right and there will be no pie for you until you calm down", would be advisable, but the experts I read don't seem to think this is the way to go.  I told you I'm learning.

Perhaps the biggest problem I have at this moment with the things I'm reading is the "validation" of things I know are not true.  This is where the advice bumps up against my morals.  I really try very hard not to lie about things.  Example: If Mom asks if I have her car keys, I hedge.  I don't want to say, "Yes, I have them", because I know it will upset her and probably cause her to spiral into anger and a rant and make her terribly unhappy, so I hedge.  I try to avoid answering the question directly, but at the same time I try not to lie.  I'm told the best technique is to give her the answer she actually wants, then to redirect her.  If I did that my response would be something like, "No, I don't have your keys.  I bet they're in your room and you can look for them after you have a snack; care for pie?."  That feels like a lie to me.  I wonder if God sees that response as a lie or if he understands and sees this as simply a technique for dealing with someone who often lives in a different reality than the one around her?  I'm sure some people find it odd that I would question this, but I do.  The Bible is pretty straight forward about lying.

This bothers me.

Thoughts?