I left two friends alone at dinner because I secretly wanted to set them up

They both agreed to a three-person dinner. Halfway through, I pretended I'd forgotten an errand and left them together.

I'd been sure they'd get on. Both had mentioned wanting to meet someone, and I thought an introduction would feel less awkward without calling it a setup. One of them had also told me she didn't enjoy being surprised with possible dates. I decided that meant obvious, formal setups, not the clever version I was arranging.

They finished dinner, exchanged numbers, and then she messaged me: 'Please don't do that again. I knew what you were doing.'

The exchange of numbers is the detail I keep using to defend myself. It doesn't answer what she asked. Should I tell the other friend the plan was mine too, or would that embarrass them both unnecessarily? I want to apologize without celebrating the result as proof she secretly appreciated it.