She does not actually think that, at least, deep down she definitely doesn’t.
I am now 23 and at the time had undiagnosed ADD but I can clearly remember saying this to my mother. Not on purpose to make her feel bad but subconsciously to get the reaction seeing how much she cared and to get the overload of reassurance that it was all okay. I always knew my mum didn’t hate me. As a 12-15 year old girl, my mum was the most familiar person to me so it was where I could and would release all my emotions. I remember hating the bad behaviour too and feeling awful after it happened and like I could not control it.
It will get better! The comment above from Anne seems very helpful.