I got a letter from the abuser my mother defended.

I 32F received a letter today from an old "family friend" that is in jail. The letter was an apology for what he did to me as a child. Without going into details, I went to my family at 9 years and told them this "family friend" 24 years had SA'd me for them to say i was acting out due to my parents divorce. What really hurt was the fact during my younger years I tried to tell my school counsellor and a close friend only for them to tell my mother who turned around stated I was lying and it was for attention. I didn't know this at the time but that "family friend" told my mum that he accidently grazed me walking by and I panicked and she just accepted that? I really started to doubt myself, and even thought i had imagined it which now makes me want to bawl because what 9 year old comes up with that? The most ironic part was I experienced symptoms of a child of CSA which my mum stated was due to trauma of the divorce and me acting out which I just eventually accepted?? I feel so brainwashed and hurt. I don't even know what my next steps are, do I throw the letter at my mums face? I have 3 children now and I don't want them to know this dark past of mine, worse yet even if i show my mother the letter what if she denies it and I'm once again just a kid "wanting attention".