She is pregnant with another man’s baby help

Okay honestly I’m in a very awful position. I’m wondering what you ladies would say/do if in my position.

Okay so I have a close friend of over 5 years now. We used to be really close at one point, but I have kids she doesn’t and we live very different lives now. We still talk and will see each other sometimes but not often. My friend, she’s married. Has been with this guy for like what 8 plus years? They had a very toxic relationship for the first few years now it’s not. It got better but He’s not providing things for her she needs emotionally, instead of just leaving she started having an affair.

She was sleeping with this guy she used to be with at some point in her past. She got pregnant. Here’s the thing, her and her husband have tried for years to conceive a baby and they had no luck. Her doctor ended up saying last resort would be IVF. she desperately wanted a baby. They never went through with it due to it being extremely $$$.. So back to the affair, basically she got pregnant right away with this other guy.

She’s been telling me everything and is venting like crazy more then I think ever. I’m here to support her, at the same time. I feel guilty knowing what I know. Her due date matches up to the guy she was sleeping with NOT her husband! She has already made up her mind that she is not going to tell her husband AT ALL in fear of him leaving but she’s gonna just make him think it’s HIS. He knows she is pregnant but thinks it’s his baby!! And it’s not. She won’t stop calling and texting me and wanting to meet up because this is a really bad situation and shes really leaning on me here for support and I’m struggling it’s all so wrong and heartbreaking. I don’t know how she can just let her husband think another man’s baby is his, and it gets worse. She’s still sleeping with the other guy and isn’t gonna even tell him it’s his. When she starts getting bigger she’s gonna block him on everything and thinks he’ll never know.

I don’t know what to say or do anymore. I’ve tried guiding her in the right path, telling her she should just be open and honest with her husband. She’s so wrong for letting him think it’s his. My husband told me I need to tell her husband. I don’t feel like that’s my place to say anything but at the same time it’s eating me alive knowing this man thinks he’s having a baby finally after years of trying and it’s not even his.

Should I stay to myself, let her still vent this to me? I don’t wanna be the asshole and cut her off but my mind is racing. I feel awful.