before his last performance too

Okay, maybe I’m just being a clueless fangirl here, but I’ve never quite understood how “why didn’t Darth Vader sense/identify Leia in A New Hope” is even a question.

Luke was on the Death Star with Obi-Wan Kenobi.  Darth Vader ended up looking straight at the kid, not too long before Obi-Wan performed his last unnecessary strip tease, and he didn’t seem to identify him.

During the Death Star run, he could sense Luke well enough to tell that the Force was strong with him, but he didn’t know at the time that Luke was his kid.

So why would anything be different for Leia?  Vader doesn’t know either child when he comes face to face with them.

It’s certainly not evidence for Leia not being Force sensitive.  Assuming that Vader can automatically sense anyone’s Force potential even if they’re not actively using it (which didn’t seem to be the case when he saw Luke, while killing Obi-Wan), why would he comment on it?

Per their dialogue, they’d met before.  So if he did sense her force potential, he would have already known about it.  And given that she was a prisoner and he was intending to get information out of her, he’s certainly not going to comment on it then.  “The Force is strong with you.”  “Ooo, that means I can use it to resist you!”

It just seems like a complete non-question to me.