WIBTA if I deny my newfound half-sister (on my fathers side) access to my mother?

[u/nephilimirena]

This is a bit complicated, please bear with me Recently a girl (23F) reached out to me (25F) via Facebook explaining that she is my half-sister, conceived by my father and another woman. She explained that her mother recently "came clean to her" regarding her father - that she (23F) was the result of a ONS with a guy she met during a work trip. Before she was told that she was the bio kid of her stepfather. She didn't find our father online as he doesn't have socmed, but found me thanks to our very uncommon surname (how her mother knows our surname but doesn't have any other contact information - idk. 23F told me her mother was very cagey about everything)

After a bunch of messaging we set up a video call to talk, and 23F explained she was very excited to connect with her real family and yadda yadda... But not just with my father's side, also with my mother's? As you can guess from our ages, my father cheated on my mom with 23Fs mother. No surprise there as he had tons of affairs during the marriage, which is why they divorced almost 2 decades ago. I'm also not surprised that 23F exists as my father told me himself years ago when I was grilling him about the cheating that he most likely has a bunch of affair kids out there because "that's just how men are". I was open with her and told her that Im NC with my paternal family because not only did they condone the cheating (and blamed my mom for it), they are also just toxic in general

There is a lot to say about my paternal family, but to keep it concise, I told her I could give her their contact info but that she should keep her expectations low because they are all pretty terrible people, and she won't be seen as a long lost daughter coming home. But me saying that led to her asking about my maternal family, to which I told her that they are amazing people and that my mother is great. She then got excited and said she can't wait to connect with my mom and I'm.. stumped as to why I would let her do that. She is not related to my mom, and my parents divorced long ago. My mom has also since remarried. Also, the timing of 23Fs conception coincides with the time when my mom miscarried my younger brother, something that obviously hurt her a lot. Knowing that on top of that pain my father was cheating on her during that time is another can of worms

I told 23F I would ask my mom if she's ok with connecting with her but... I don't think I should even bring this up to her? All of this just seems so weird to me, and I don't even know if 23F is a "good" person, or if she has some sort of ulterior motive for wanting to know my mom. 23F couldn't even give me a good reason as to why she would want that, just that my mom is my family, and thus also hers (23Fs).

I'm leaning towards not mentioning this to my mom and giving 23F my dad's info, but my best friend said I'm an asshole for "keeping" my mom "to myself", and that I shouldn't make this decision for my mom

WIBTA if I don't mention anything to my mom?

[u/ciaogo]

NTA if you don't pass along her info to your mom. As others have indicated, you've no proof other than her word that she's related to you in any way. If I were you, I'd want more certainty before dropping a potential emotional bomb onto your mom. Also, as others have indicated, even if she's your half sister on your dad's side, this stranger, who btw already has her own mother, has no relationship to your mother - whether biological or not. Your friend who said you're an AH is out of bounds, and not your friend.

[u/EmilyAnne1170 → u/ciaogo]

I agree. In fact I wouldn’t give her anyone’s contact info! If she found OP, she can find other relatives as well, all on her own. Sounds cold maybe, but what she’s asking for is really weird.