What does the term "deflection" mean?

I need help understanding a term my therapist has used to describe conflict with my wife. She says my wife routinely “deflects” her issues on to others as cause. I don’t really understand how this works and was hoping someone could explain?

After I accidentally discovered my wife had sent over 1000 text messages and emails to another, younger man over 3-months, I calmly confronted her and she denied everything. I showed her records over several months showing her doing this she lied several times and then admitted she had done it, but it was because of how I treated her. She decided to give me her phone to see there were no texts, but after she gave me the phone I mentioned it was fairly easy to recover deleted texts. She became enraged and demanded her phone back and became very physical with me by hitting me repeatedly. I have never hit her, ever. I gave the phone back and she promptly destroyed it and then drove off to throw it away somewhere unknown to me. She has repeatedly said what she did was all my fault and said I needed therapy for all my issues.

My therapist has a Phd and after many open and honest talks has said my wife routinely “deflects” her issues onto others as the cause for her actions. My therapist has said this seems like a classic case of “deflection” and I (and/or others) are not the real cause.

I don’t really understand this and hoped to find out if this is a real known Psychology issue, term, condition, or whatever. How do I handle this and what is the likely future outcome with my wife? My wife tells me I have big issues with anger, drinking, and drugs (I used to very occasionally smoke pot – very little and not often and haven’t for a long time). I’ve never been abusive, mean, confrontational, or missed events or other similar things and have always been called “happy” when I did drink. I asked my wife about the anger issues and she says I’m always like that, but the only examples she had were arguments we had 10-15 years ago. I never considered myself a heavy drinker and easily stopped 6 months ago to go with a general effort to lose 10-15 pounds and because I didn't think continuing was a big deal.

This was way too long and if you got this far, I apologize and thank you for your interest in helping. Any knowledgeable help or feedback would be greatly appreciated.