Display Moremate, whilst your argument is solid, and all the results and deductions from it are sane.
Your foundation is wrong.
This is K-pop, emphasis on the K.
In SK, they are called girl group. Yes exactly those two words. In English, not Korean.
Even when talking about a single member of a girl group.
It's a title. Not a fact.
That's why I am saying separate the context,
If the context is K, then sure Girl Group, else just Musical Act.