Sister having sex with a much older man?

My mom has a friend who has a promiscuous dad. Two days after my sister turned 18 he started sending her messages and invited her to her house and seduced her. She was sometimes going out and didn't tell us where, but I sneaked to her room whens he was taking a bath and saw messages between them on her laptop.

I told my mom and she got angry and her that he is just using her and that he is way too old for her. She seemed to feel a bit bad. My mom told her friend what her dad's been up to and and her daughter said its their business since she's old enough to know what he's doing.

What is your opinion?

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+1 y
he's 56 by the way
Sister having sex with a much older man?
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