Hi Mickie
5 amp seems too low a rating for a lathe. Look at the size of the motor and whether it's induction or not. If you don't have a manual there should be one on line which will tell you what fuse to use.
However, the fact that it popped your main electrics is worrying and suggests a short circuit of some kind so personally I'd have that checked out first. If she bought the lathe from a shop then ex demo or not, your entitlement to make them sort it is absolute and it would be my first point of call.