I think what happens is, IQ is a sort of speed. They teach the class assuming they can get most people through it at whatever pace they are used to teaching at. If you're quick, you can keep up with a below average effort, and vice versa.

As you get higher and higher up in the stratosphere, the balance between "we need enough students" and "we need to go faster" ends up favouring the few super intelligent people, along with the people who can arrange their lives to put in the hours.

That's not to say you can't learn something if you are slow. You just can't learn it at the pace they are teaching, and you might not have the wherewithal to learn it at your own pace.

So to you it looks like this lady would never learn it, but I would guess if she had a personal tutor they would be able to pace it.