AITA for being “cruel” about my dad’s ex and her “medical need” for her implants.

I’m a 16 year old girl and I have 2 siblings (19F and 30 year old F) , my dad is 53 and he got divorced when I was 9 because he cheated on my mom with this one lady who I despise. I only found out myself last year (she’s not the reason they got divorced though). <br><br> My mom says she wasn’t the reason but my dad did cheat with her and my mom has said she was a “trigger” . I don’t really understand so I’m not in touch with my dad. <br><br>Out of the blue he met someone new when he started working with her and she’s 35 and she asked him to pay for her new implants as she wants bigger ones and wants to go for the high quality implants that cost 9k. She said she wants them for medical reasons as she’s underweight and it would be better for her. <br><br>I don’t know if it’s true or not. It looks more like an excuse for me. I have no idea why my dad would fall for that when he said no to my older sister when she asked to get a breast reduction so she could sleep better but he said no because he said she’s fine without surgery. <br><br>I said she looks full of shit for saying it’s medical and that my dad’s a fool if he believes it. My sister said I was being harsh on my dad and that maybe she’s telling the truth but I don’t see why he’d believe that when I asked for surgery for medical reasons years ago. <br><br>My sister said I’m being cruel but I don’t think I’m being too harsh on my dad. I think he’s being cruel.