Ms Sapper was raised in a home devoid of love and affection and yearned for the care Leifer purported to be providing.
"Faced with the painful truth that her love wasn't real was a betrayal of such magnitude if left me broken," Ms Sapper told Leifer in a pre-sentence hearing in the Victorian County Court on Wednesday.
Leifer, the former principal and head of religion at the Adass Israel School, was convicted in April of sexually abusing Ms Sapper and her sister Dassi Erlich when they were students between 2003 and 2007.
A jury of six men and six women found her guilty of 18 charges including rape, indecent assault and sexual penetration of a child aged 16 or 17.
The 56-year-old mother of eight was acquitted of nine charges, including five against the siblings' older sister Nicole Meyer.
Leifer appeared in court by video link from the prison where she has been held since extradited from Israel in 2020.
Ms Sapper struggled to quantify the impacts of the abuse on her life.
But supported by her family and friends, she refused to let the broken fragments of herself define her entirely.
"I will not allow my abuse to diminish my present, or my future," she said.
Ms Erlich said there were no words she had wanted to hear more than when Leifer told her she loved her like a mother.
The insidiousness of the abuse perpetrated by Leifer against her fractured her trust forever.
"Relationships exist in a perpetual juggle between desire for connection and the echoes of her trauma," she said.
But Leifer could not break her spirit.
"Today I stand as a survivor - your darkness does not define me," she said.
"Instead I choose to focus on the light - I am resilient, I am powerful and I am so much more than the limitations you chose to impose on me."
Ms Meyer sat with her sisters in court and is expected to read her own statement outside court later on Wednesday.
A pre-sentence hearing before Judge Mark Gamble is expected to run for two days
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