Yeah, she's just playing out the dynamic of dysfunction. There must ALWAYS be a scapegoat, because no one (especially not the addict/alcoholic) can ever accept personal responsibility. She doesn't want it to be her (as the mother she's the obvious target), so she's heaping the blame on you. Not being perfect is hardly a crime, and it certainly wasn't your fault that he already had an arrest warrant that he was avoiding.
I heard the same crap almost verbatim from my ex's mom- everything was my fault, I was abusive, drove him to drink, needed to be on medication because I was crazy, I was a c and a b and every other letter of the alphabet, blah blah blah. It really did upset me, especially in the beginning when I felt like I needed external validation that I was doing the right thing by leaving.
Thankfully I was just starting with Alanon so I bit my tongue and kept my head down and she eventually got her comeuppance without me lifting a finger or saying a word. Now she does everything she can to ingratiate herself to me. I take it with a massive grain of salt, because she's not in any kind of recovery- despite all the Alanon literature I've sent her, lol- and I know that she will turn on me in a second if she felt it would be to her benefit.
I've also found this thread very helpful.
http://www.soberrecovery.com/forums/...ing-guilt.html