You don't need to pay for courses. There's countless videos even whole series that teach you Word and Excel from basics to advanced on youtube. But if you must pay, I'd say Udemy but I really don't see why you would pay when there's free.
HOWEVER, you can learn this stuff hopefully she has the aptitude to actually apply it. That is two very different things.
Seriously, I still have analysts and business managers that email me screenshots of Excel data rather than copying and pasting.