I agree, MEPS definitely does have its issues and their processes are far from perfect. But there is always multiple sides to a story, and there are folks with a multitude of issues that meet red tape when applying for a physical.
OP's story is that she's clean and MEPS simply will not schedule her. If that were truly the case, I'd lean more on the side of MEPS, but as it turns out she's been through MEPS before, been to OCS before and regardless as to why she did not make it through, there is more to her story.
But maybe that has nothing to do with it and maybe its all on MEPS. Maybe this MEPS is denying folks with no medical or legal issues physicals to prevent them from joining the military. I don't know what is to be gained from that, but maybe this MEPS is just that screwed up.
So, if that really is the case, maybe OP does need to go above the recruiting district with a complaint.
BTW - it may be different for each MEPS, but for the ones I know of, its actually less work for MEPS to work an Officer accession applicant. They do the physical and then it goes right back to the Officer recruiter to submit to N3M and apply for waivers if needed.