Does she plan on practicing medicine in the UK after graduation? Is she eligible to remain in the UK without a visa? If her intention is to go back to the US and practice, that won’t work. She will have attend medical school and fulfill residency as a physician (actually adding time rather than shortening).
Alternatively, she can study Biology/Chemistry and apply to US based Medical schools, but I do not have the information on how successful that path is for students. The school representative will know or can find out for you.
Best of luck