I stand by my advice from 5 years ago (reposted above). It was true then; it still true today.
What possible explanation can she give to adcomms for transferring to a harder college and then NOT taking her pre-reqs there?
Classes at her new school were too hard? (Med school will be way harder than any undergrad.)
Transferring as junior may be enough by itself to set off alarms for adcomms unless she has a very good explanation (financial hardship, major illness/death in the family, personal health issues). Transferring then NOT taking pre-reqs at her new school will definitely raise suspicions. True for science and non-science majors alike.
Also, if her new university offers committee letters for its pre-meds, she won’t be able to qualify for one if she takes her pre-reqs elsewhere—something she will also need to explain on her med school secondary applications.