So what you're saying is that you prefer to play the ps4 on your TV, but when your wife is using the TV you play on the monitor. You could use a switch, but you'd still have to take the HDMI from the source each time. It'll be clunky, but I think your best option is to have a switch that goes into the TV. Then attach a splitter that would have the PS4 connected to the monitor and TV at all times.