Joseph – it was many years ago, so I no longer remember. I assume that I couldn’t daven after the date because it was almost shkiya. I assume that I didn’t daven beforehand either because it was too early when I left my house or because I didn’t have time.
In any case, davening Mincha on a date is not a big deal – it takes 5 minutes if you’re speed davening – that’s not what bothered him, it was the idea that I was davening Mincha altogether.
Actually, he hadn’t davened Mincha yet himself, so we had to end the date so he could go to shul. In fact, when I told him that I had to daven Mincha, he thought at first that I was reminding him to daven Mincha, since it hadn’t occurred to him that girls daven Minhcha.