[Studio25]

...and models without the switch are even easier to accidentally disable wifi. It's a keyboard button combination.

At the bottom of the keyboard there's a button marked Fn - probably to the left of the spacebar. On the function keys, there is one with a wifi icon on it (usually F3). All she needs to do is hold down Fn then press F3 or whatever key has the picture. She should do it once and then wait for a bit - it won't yield an immediate reaction.