Caporegime
The lady I've mentioned has 5 GCSE's and no A-levels, she failed them. She started a course at college when she was 25 (think it was 3 years, I may be wrong) which then allowed her to apply for and get on to a medical degree. When I applied for St Andrews they were wanting ABB from memory although I don't think they took less than an AAB. GCSE's didn't come in to it. At least for me as they never asked to see my results.
So essentially she re did her GCSE and a-levels (3 year period) and got the required marks to get into Medicine so she is a late starter as she still need the rest of the training. I am not seeing a problem here in terms of work required.
Current UCAS requirements are (albeit this page says Hospital doctor, not GP)
https://www.ucas.com/ucas/after-gcses/find-career-ideas/explore-jobs/job-profile/hospital-doctor
What do I need to do to become a hospital doctor?
To become a doctor you need to complete a five-year degree in medicine. Entry requirements vary, but to get on a medical degree you normally need at least five GCSEs at grades A* or A, including English and maths and at least grade B in science. You also need a minimum of three A levels at grades AAA or AAB in chemistry and either biology, physics or maths, plus another academic subject. If your medical degree is your second undergraduate degree, it will be four years long.
After completing a medical degree, you then need to complete two years of foundation training, followed by three to seven years of specialist training. The length of your training will depend on which speciality you have chosen. You will also need to pass a Disclosure and Barring Service (DBS) check.
You can even see what each university asks for here, I think the minimum is AAB but most are AAA. You are right that some don't state GCSE requirements, some do, it depends on the university.
https://www.medschools.ac.uk/media/2357/msc-entry-requirements-for-uk-medical-schools.pdf
So, in terms of intelligence, you need to be smart to be a doctor, that is the metric we, as a society have chosen to select and filter out people to be doctors. You can say there are a better way to pick smarter people but this is what we've got. As for dizzy people, I know a lot of dizzy people in day to day life but they are surprisingly good at what they do at work. So unless you have seen her at work, I am not sure how accurate that statement is in terms of her overall job performance?