It's entirely possible she got a lousy education as a child, but that doesn't excuse her becoming a teacher. She knew she couldn't spell, she knew that her own grammar was lacking, she shares a large portion of the blame for her becoming a teacher.
How many people failed in her story? Certainly she did, as seemingly did her K-12 teachers and university professors. Whatever England's system is for credentialing teachers, it certainly let an elephant slip through the cracks.
I'm not able to say who owns exactly what percentage of the fault for this woman's becoming a teacher, but I can't help but find her sorta-mea-culpa in the linked column to be one big, lousy, attention-grabbing excuse.