My DS (almost 20) was the same, currently in med school (well, not exactly physically but you know what I mean!).
He got involved with literally everything to bump up his uni application - became president of the student council, read New Scientist (subscription from age of 13), volunteered at the local hospital for two years (from age 16), did NCS, got work experience shadowing a GP (rare as hen's teeth, he was flipping lucky!), volunteered in a care home, volunteered in Kenya, bumbled off to Denmark on a whim, went to an international school council thing in Rome, travelled round Scotland, you name it, he did it. He's currently working with vulnerable adults in a care home when not studying. I often wonder where he came from...think he must have been switched at birth, but then I had a home birth so....??!! 
When he started science in Y7, his science teacher told the whole class that no one there could expect to be a doctor or a vet so forget that. I soon had a word with that teacher and the HOY for knocking back ambition instead of supporting it!
Support your daughter as much as you would with any other ambition. Get extra tutoring if need be (I did for DS's A level chemistry), encourage her to leap into anything and take every opportunity presented to her. Actually, as parents, we should all be doing that anyway! 
Whatever she ends up doing, she'll know she has an amazing and supportive mum, OP!