Medicine and law are such disparate subjects that my heart always sinks when a prospective student approaches me and tells me that they want to study one of the two subjects.
Invariably, it seems that the student is
a) under the impression that a law degree is a golden ticket to a good job - it isn't, given that demand far outstrips supply of training contracts and pupillages. If you don't get a TC / pupillage, then essentially a law degree is no different to a history, English or politics etc. degree.
b) the student is going for subjects that they think guarantee a good job, without thinking about where their interests and skills lie
c) the student's parents aren't particularly well informed about the graduate careers market in 2016. The reality is that 70% of graduate jobs are happy to take people with a degree in any subject because they are looking for the transferable skills that they've learned on their degree. For instance, I work in marketing and have a degree in a completely different subject.
I would recommend that your DC
a) chooses a degree course that they will enjoy - this is paramount, because if they don't enjoy it, they won't work hard. This invariably ends in disaster, either because they drop out, or they get a low grade. Doing a degree that you don't enjoy is an expensive form of misery, and when it's a vocational degree with a clear career outcome (e.g. medicine), it invariably turns out to lead to a job you don't enjoy.
b) thinks about what career options they might like to consider for the future, and makes sure that they aren't closing off paths that they want to keep open. Don't forget that, for instance, if they did want to go into law then it's entirely acceptable to do any degree subject followed by a GDL conversion course.
Bottom line is, let the DC choose a subject they love. It will turn out fine in the end!