Touch screen help

Hi all.

My wife's s4 mini started to play up, 1/4 of the touch screen from the bottom has stopped working. this means she cannot assess app tray, call log etc.
the screen itself looks fine and all other parts are responsive to touch.

I manage to reset the phone by turning it sideways to assess all the keys but this has not solved the issues.

Do I need a new screen or can this be repaired?

thanks