She was sexually abused in childhood.

Im currently dating with a beautiful girl of 19 years old. She shared some story of her life. 1. She was sexually used in her childhood by her own brother who is 8 years older than her! 2. She lost her virginity when she was 11 years old by that person. 3. She is being sexual rltnship with her 8 yrs older brother since then like 8/9 yrs. 4. Now she feels ok about it and it has been consensual. I guess she got some obsessing mind over it bt she shared it to me 5. She lost her father since child nd her mother doesn't care abt her. They r 2 twin sis nd 1 brothr. This  happened to only her! 6. She told me she doesn't want to get married soon. She doesn't want to meet any psychologist either. NOW I CAN'T FEEL GOOD ABOUT IT!!! Should I let her go??? I feel fear to fully stop talking cuz then her brother is gonna be more benefited if she is not talking with any other guy! WHAT TO DO NOW , SHOULD I BE OKAY WITH IT ? MY MIND IS HURTING!!! PLZZZ HELP!!!