Why?
Because,
a) As you say there may well be “Windows specific software needed,” buying a Mac to run Mac-specific software hasn’t existed in decades.
b) A student with a desirable piece of tech is liable to be a target for theft.
c) If she’s not used to it, the OS is one extra thing to learn on top of everything else.
d) The instructions provided by a lecturer may well differ from what she’s seeing.
e) “Buy a Mac to run Microsoft Office” said no-one ever.
f) Why would you pay an Apple premium for a student laptop? What would it gain outside of fanboyism?
g) Where are you finding £400 Macbook Airs?
h) The first time she drops it, it’s f’ked.
i) The first time she wants to upgrade it, well, see h).
j) Need I continue? Macbooks have their use case but “my daughter is starting college” is not one of them.