The delay seems to be caused by the number of commands and submenus. It's annoying, but I don't think there's any way to make it faster. However, it does not make the game impossible to play. Just pause the game whenever it needs extra time to bring up the interactions. This also helps when you need extra time to search through the submenus for a command or interaction.
You can pause the game quickly, and without interrupting what you're doing with the mouse, by pressing 0 (number row), 0 (numpad), p, or ~. I prefer the 0 (numpad) because of it's larger size and convenient placement on my fullsize keyboard. I do this quite often during conversations.
The problem is I have this delay every single time I click on a sims, even the one I'm currently controlling. I wouldn't complain about it if it was occasional, I already had to pause whenever I wanted to use the fridge for like the past two years...
