Well, that would depend on which way up she holds the camera! :)
I've got a 19" Widescreen and it's great - my first TFT too, my old monitor is 19" CRT which is HUGE and HEAVY, but it can handle much higher resolutions up to 1600x1200, but I use it at 1280x1024 because any higher and thin lines and small text get a bit blurry. The TFT widescreen is best used at it's highest resolution, which is 1440x900, as it looks really clear, use anything lower and the picture gets stretched to fit and so single pixels are doubled and it looks messy. You have to pay £££'s more to get any higher TFT resolution than that.
I would suggest widescreen - they look nicer together as a pair (you are going for a dual-monitor set-up aren't you?).