What Genie99b said. Good advice, certainly.
Notwithstanding, at the same time, if your daughter is sure she
would like to give the Medical School route another shot, she can
try a route less conventional : for one year, do not go to either
JC (arts) or Poly (non-biomedical), but instead self-study and
retake O levels as a private candidate, *and* self-study A levels
at the same time (since due to age constraints, she won't be
allowed to take A levels as a private candidate till she's
older).
If all goes well, her O level results should improve sufficiently
to re-apply into a JC which allows her to take Science. And
meanwhile, her self-study of A levels would have prepared her well
for her JC studies.
Worst case scenario, she can always (whether at the time she's in a
JC, a Poly, or neither) take A levels as a private candidate. If
she manages to achieve all As as a private candidate, she can still
apply into Medical school (both local and recognized overseas
Unis).
The above is for your daughter's and your own consideration. It's
just one possible route. I mention it, not because it's necessarily
any better or any worse, but only because it doesn't even occur to
(or register in the minds of) most students and parents, that this
(albeit unconventional) pathway could actually work.