Although she has the right grades, Biology is a requirement for the BM6 programme as far as I know. (I think there was talk of accepting those with Bio and Chem at AS level if Biology wasn't taken to A2, might want to ring admissions.)
http://www.som.soton.ac.uk/undergrad/course/bm6/entry/A levels:
A level grades BCC including chemistry and biology (or equivalent qualifications). Subjects with material that overlaps (e.g. biology/ sports studies, mathematics/further mathematics) may not be offered in combination at A level. General studies and key skills are not accepted. We will not consider individual unit grades for A and AS levels as part of our selection process.
She would have to do the UKCAT to apply, however they don't really use it (though I think it's becoming something they use to differentiate between students, unlike BM5 where there is a cut off).
There are also non academic requirements of meeting two of the following:
First generation applicant to higher education
Parents, guardian or self in receipt of a means-tested benefit
Looked after young people living in supported accommodation
In receipt of an EMA (Education Maintenance Award) or similar grant
Living in an area with a postcode which falls within the lowest 20 per cent of the Index of Multiple Deprivation (authenticated by the University), or a member of a travelling family
If she doesn't want to do Biology, there are other access to medicine courses aimed at non-sciencey A level applicants.
My only concern for her would be that medicine and med school is riddled with exams, however with the support offered at uni I'm sure she'd be supported through her exam worries!
Hope this helps!