Potential 'mare.

[telectrix]

An RCD FCU just for two bedside sockets likely to have a table light and alarm clock plugged in?....in an upstairs bedroom?....nothing else in the house on an RCD??......complete muppetry.Either tell her the whole place needs upgrading and is not safe to extend....
Or.....as long as the existing is capable of being extended (loading wise) and is earthed I'd just do it if it was my mother......It's been like it decades without a problem,two bedside sockets is hardly going to change that.

i quite agree, pointless excercise, but regs. say new sockets must have RCD protection. common sense says why bother.