How much do Med schools look at GCSE grades?
All unis have their own entry requirements - choose a couple to start with and check on their website to see what they require. You'll soon realise you need a spreadsheet to keep track! You'll also discover that entry requirements are the bare minimum; you'll need to look carefully at shortlisting criteria for interviews to see how your DD scores. Some unis base their interview shortlist purely on UCAT ranking, others use a combi of GCSE points, predicted grades, BMAT/UCAT score.
What subjects should she do for A-level?
Check websites to make sure. Biology and Chemistry usually means she's safe for all unis.
Does she need maths A-level?
No. That said, Oxbridge stats show applicants with these 3 subjects stand a better chance. Maths will also help with UCAT and BMAT tests.
Is IB or are A-levels preferable to Universities?
No difference.
Should she be doing relevant work experience already?
She should start now. DS1 volunteered as a ward assistant for 4 months when he was 16. This led to a week's work experience - all departments including surgical observations. Check if hospitals nearby if they run student programmes. He now volunteers weekly at Children's Emergency and has direct patient contact.
What sort of work experience is useful/viewed well.
Any caring commitment is good. I am assuming that your DD is 16 already - she should start volunteering at care homes etc or community groups which have a caring element. DS1 volunteered with Riding for the Disabled (when he was 15) and St John's Ambulance (started age 12). He also used the time after GCSE exams to find a job (pharmacy) and has kept the PT job going (still there now). It is good to show long-term commitment.