That is terrible.
One thing is to be abused by one member of Your Family.
Even worse is to be abused twice by mother not believeing!
You Write:
"My cousin whom I tried to hide with that one day tried to come out and tell her mom what went on when we were little and she was told she was making stuff up."
If that cousin's mom was in the same Family, maybe she was the one abused when she was little?