Do I tell her?

Today I went to the gym, and one of the girls I usually worked out with was there. We had a class together and We’ve talked and hung out a few times outside of the gym but we aren’t like best friends or anything. Anyway she asked if I could give her a ride to her boyfriends place because he had her car and was going to meet him there instead of waiting for him to pick her up.

So I agreed, she said it was close by. Anyway Im getting there and I recognize the street. Then we get to the apartment buildings and I recognize it. I said “funny I know someone that lives here” and she just said “Oh cool, my boyfriend ‘Josh’ just moved in so maybe we’ll see each other around.” Then she gets out and I see the apartment she lets herself into after grabbing a key from a plant.

Guys. I know ‘Josh’ , I know that is in fact the same ‘Josh’ because I know that was his apartment she went into. He is my cousin’s boyfriend. She’s currently pregnant and had me drop her off after one of her appointments and they let me in to show me around the new place. They dont live together , I think she’s planning to move in sometime before the baby arrives but this was literally a couple weeks ago.

I have no idea what to do. I tried calling my cousin but she’s at work apparently according to my aunt.

Do I tell her? Is it not my place? We’re close in age only two years apart and grew up basically as sisters. I think she might even know this girl through mutual friends but idk. If I tell her, how do i do it? I need advice. This is a delicate situation. Not only is she pregnant but she’s family. I dont want to screw this up. But i know if it were me I would want to know. HELP