How to make sure she wont do this again , plz help ?

i asked people about this and all they told me was to leave her , but thats not wat i want to do , i only want to make sure she wont do this again , so here it is;
am a 20 yr old grl i live w/ my 42 yr old gf , regardless of the age difference we both love eachother very much , however her parents seem to dislike me so i got into a fight with her mom which led to me verbally insulting her , and when we got home we had a fight about it which got even more and more tensed and then for the first time she physically against my will held me down like used her weight to pin me down and hit me( spanked me , not in an erotic way so plz no kinky comments) . but its still consider hitting. my wrist is bruised now, and i repeatedly told her to stop hitting me as she was hurting me but she didnt stop not even when i cried, i have never seen her react this way , shez a very loving n nice person no matter what ne one says i know shez kind and loving , she says she goes through hell trying to defend "us" without having to worry about me acting like a "brat" even though i was only defending myself her mom was obviously trying to tick me off , i honestly as insane as it may sound believe her mom told her to hit me , cuz she has never done such thing like this before. how to make sure she wont hit me again? like do u suggest an anger management class or what ? plz help , thnxx
PS. i dont want to break up with her over a one time incident like this. and this is serious so plz no kinky responses.