After having been" controlled " throughout her short life,,it was Sheilas' turn to take control,,and that's exactly what she did !
For a mirror image of Sheilas' life, read about Elizabeth Haysom in Murderpedia. Middle class family whose expectations of their daughters' higher education,first at boarding school then on to greater things,was a turning point in Elizabeths' behaviour.
Elizabeth wasn't adopted,but saw her time at boarding school one where her parents " wanted to get rid of her ".
If I remember rightly,this began in 1985/6.