The issue is not whether overseas medical school training is better or not. Some is, some isn't, and with the recent expansion of medical education there are question marks about the quality of some of the medical graduates that the UK produces. (One recent change is that merit has been taken out of the process of allocating Foundation places, whilst Foundation performance and references do not contribute to achieving a training place or a local hire job.)
Even still the quality of overseas grads, whether British citizens or not, can be worrying. Dd certainly came across one who appeared to have no medical education at all, whist others have had very little patient contact because they studied in a country without English speaking patients.
The NHS issue is that all applicants have to be treated equally. Both DD and Beth cannot compete with doctors offering 10 years or more of experience. The concessions on expedited family settlement means that entry level locally employed jobs will often attract several hundred applicants, some of whom will be seriously overqualified. The NHS also prioritises those with significant research and academic qualifications for specialist training places. (And would only have enough training places for about 10% of the cohort even if half of those places were not going to medics from overseas.) It is much easier for those who are able to take a couple of years off to prepare at a specialist college oversees or for those working in a London teaching hospital with a lot of research going on, than those working night shifts in Fife's A&E.
Australia in contrast puts a lot of emphasis on references and experience. They seem more interested in those who can cope with a busy ward, than how many times you have your name on a research paper. Both DD and Beth have done well to be accepted there. Weirdly the ultimately aim of many of the overseas doctors DD currently works with (and all the SHOs in the department where she is locuming are from overseas) is to get to Australia. She in contrast would like to stay in the UK. But because of the different recruitment criteria she has to leave and they have to stay.
The same may well apply to Beth.