It's so good to hear she enjoys her subjects but just bear in mind she'll need to do her y12/13 vet med work experience which usually happens on weekends for a set period, 4 of the hardest a-levels and keeping good work-life balance. (she might also want to try a part-time job which could limit her time for school work on the weekends).
I would recommend she starts with 4 and then check in after a few weeks to see if she still enjoys them all and isn't missing assignments or behind on her work, I've known people to drop an a-level to help their well-being before so she should keep a good sleep schedule and her mental health is the most important thing,
I went to a school where most people did 4 A-levels and I felt like if I gave one up I was somewhat "not smart enough", which is totally not true!!! your daughter must be super intelligent to get those GCSE grades,
On the other hand, doing 4 A-levels will help her enjoy school a bit more and give her a variety of degree options, I've known people who went into A-level sure of one career path but enjoyed one subject more than they were expecting and studied it afterwards, and more competitive unis tend to choose students doing 4 rather than 3 a-levels.
From a student's perspective, I'd keep an eye on her turning in assignments, deadlines, and stress levels. A more practical way is by adjusting her schedule so she has more hours to do school work i.e. if she does any sports or extracurriculars she may need to limit the hours spent on them to make time for her studies and help her keep on top of her deadlines by making a timetable for school work hours and a balance other commitments, and if her grades are getting low and she's missing homework or feels too pressured I would recommend she dropped one.
I'm not sure how helpful this is but I d