Manmust

I've been seeing her over 3 years now. I've complained she looses control while drinking shortly after seeing her. Things got better. In the past year, I get uncomfortable with her going out without me. Doesn't come home when she says she will, drinks in excess, then drives.
It's been a few months since she's gone out without me. Today, she rides in a parade with her son while I work. I get a text after the parade that she got rear ended and the guy is claiming she backed into him. Then tells me she contacted her police detective friend and its being handled. Apparently they contacted the officer responding and blamed the guy for rear ending her at a stop sign. She calls me and tells me she backed into him. I could hear she had been drinking. Her 13 year old son was in the car. I confront her at home. I question why she lied "so that you wouldn't blame me drinking"
She tells me 2 drinks at first, eventually adds another....but this girl requires 4-5 before you can even tell. She said she would drink again if she had to do it all again, but states she would have eaten more or avoid the detours.
She says she's not changing for anyone. Says she is incapable.

Also, 2 years ago, a cop pulled her over...he could tell she was drunk, but if I came to pick her up, he would let her go.

Am I over reacting?