> she uses the socket on the same switch box for the washing machine
I am not an electrician but AFAIK electric ovens need their own connection to the fusebox and operate on their own dedicated 30 amp or 45 amp circuit. The idea that she's plugging it in to a socket, and sharing that socket with a washing machine, sounds all wrong ... no wonder it's tripping!
I would imagine that the cooker and the washing machine are both fine but you're asking the circuit to do too much. I'd unplug the oven until I'd spoken to an electrician, but the washing machine should be fine to use.



