Meg, the Spitter!

So Meg busts in from school the day before yesterday just bawling. I am like what is wrong, and she says I had to pull my stick today. (This is their behavior system at school.) So, I asked her why she had to pull her stick, thinking it would be for talking, and she said because I spit at C. I said you what, trying not to totally lose my temper. Then I precede to try to get the story from her, why would she do that blah, blah, what exactly happened, etc. So she said it was an accident she was just talking and accidentally spit while doing that. So I told her we don't do that blah blah, grounded her from the computer for the night, and then called my mom to see if her teacher said anything to her when she picked her up. Mom said no but she would ask about it. Yesterday Meg comes home and mom tells me what her teacher said happened which is a totally different story than I got from Meg. She spit at 2 girls and she did it because she was mad they were playing together and then when one of the girls laughed at her for getting her stick pulled she hit her. UGH! So, she lied to me which in my house is an infraction of the worst kind. I mean they know punishment is going to be way worse if they lie about it. So I grounded her from the computer for the rest of the week and she also got a spanking. She also has to apologize to her teacher, as well as the 2 girls. Which she has today to do on her own or I am going up there tomorrow. I was just floored that she would do that, and feeling like a failure as a parent. She knows better than that! What the heck was she thinking?!?