Mom's been having an affair, do I tell dad?

I think my life is a mess at this moment. I (16 F) caught my mom texting things to her male friend from work. She was shocked and tried turning off the company. It turned into an argument and she started crying, telling me to don't tell dad, to cover up for her, to lie for her. She's been having an affair and isn't planning to stop. Confirmed.

It's been a week and I can't keep up with it. I'm their only child and also close to dad. He's already noticing that my mother and I are having arguments ever since.

I feel that if I continue covering up for her and he finds out, then I can possibly lose a lot. I got reminded of a similar story that happened many years ago. The girl was my age too (also an only child like me) and covered for the mother's affair. Then the father divorces and disowns his child after she turns 18 and never speaks to her again and she's been trying to reconnect with him since. I don't want that to happen to me. What do I do? Tell on her?

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I feel trapped. I love my mother too but dad doesn't deserve that, no one does.
Mom's been having an affair, do I tell dad?
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