Computer monitor burnt out

I think the light in my sister's computer monitor burnt out. The monitor is on, but it just looks black. However, the reason I think the light has just burnt out is because if I shine a flashlight on the monitor, I can see what the monitor is displaying. So the problem isn't that the monitor isn't displaying anything, it's that the light in the monitor isn't working, which makes it extremely hard to see what is on the screen.

So is there any way to fix this?

you need a new monitor.

Before you head to the shops, do a quick check of the monitors settings. To make sure your sister wasn't messing around and accidently turned the backlight off.