Restaurants splitting checks seems to be a regional thing. I know in Australia, most restaurants refuse to do this.
I'm not sure why you didn't speak up and say, "Oh, but you weren't planning on paying for me. I'll buy my own dinner--I expected to, anyway." And without any conversation, or regardless of it, simply hand over the money.
This is what I have done in the past - works beautifully, and avoids the awkwardness.
I think this would have been the best plan. That said, if Priscilla got vocal, and insisted that she'd pay for your meal, I wouldn't press the issue. I'd gracefully accept, and make a note to treat her to a meal at some later date.