Girl i know from high school

man i have known this lovely girl for about 30yrs and she is lovely with long blonde hair 44dd tits and nice ass..i am friends with her whole family and we dated some over the years...i always thought there was something off about her with mood swings and things and sometimes talking about certain things she would act strange..after her mother divorced her father her mother confessed to me that her daughter had been having a sexual relationship with her father which she finally told her mother about....it had went on for several years i never would have guessed and i have never told this girl that i know.i would like to see her again as we are both single now but don't know weather to let her know i know about her past. She a son that is about 19 i wonder if she carried on the lessons that her dad taught her