WordNet
functional illiterate
n. a person with some ability to read and write but not enough for daily practical needs
Usage examples of "functional illiterate".
There was Lieutenant Wordly, who spent as much time holding on to a puke bag as he did the stick, Jefferson Washington Jones, plane lover, GED graduate, a functional illiterate until he was twenty-five, whose first solo, at the age of fifty-seven, was in a jet trainer, and all the others.
Just from that, I guessed she was probably at least a functional illiterate.