Is it wrong of me to discourage her?

My dad is a toxic alcoholic who shows a lot of narcissistic traits. (CPS always throws their case and I heartbreakingly cannot take them in, before anyone asks). I moved out when I had my daughter because I couldn’t take all the drama anymore. Well after my mom almost left, he’s trying to show her that he “changed” (which I know is all fake because he does this a lot. I’ve seen it at least 5 times this year alone). One of her complaints was the lack of time he spends with the kids. SO he’s been buddying up to my little sister - she’s 16 and has had a extremely hard time with the trauma he’s put her through over the years. He bribed her with $200 to hug him and is offering to buy her a bunch of electronics.

She told me about it, said she still isn’t okay with him, and asked my opinion. To me, it instantly raised a red flag because I feel like he’s trying to buy her affection and love. I want to warn her to be careful but I don’t want to be the reason she doesn’t have a relationship with him if he is being genuine this time.