Starby....first of all it is no big deal...not a life threatening situation in any way.
It is almost certainly a viral infection to cause such a sudden loss of sense and smell and itis a matter of chance as to if they will return.
A sinus infection or an allergy may have caused this and if so her taste and smell will return following the appropriate treatment.
However i must stress that a viral problem is the likeliest cause.
Yes, go to her GP and ask for an ENT referall.