Ah, I see you’re in Birmingham, I’m on the Fylde coast, I was going to offer a lesson as I’ve taught hundreds of adults to ride – you’d never believe how many can’t. Bit too far away from you unfortunately.
If you can find a bike to borrow for her to try, don’t even worry about taking the pedals off, just put the seat very low and get her to “scoot” along with her feet, trying to see how long she can balance for. Once she can balance, she can pedal! Oh, and always the first thing to do is get used to the brakes, so scoot, brake, scoot, brake, repeat.
If she has learnt before, no matter how long ago, you’ll probably find it all comes back very quickly.
Good luck to her 🙂