Yes sometimes management is eye-ing one or a few members more closely than the other members, BUTTTTTTTTTT still it comes down to the girls and their ego(s).

If the girls had a pact to try as much as they could to not let management not single out members into being possibly future solo artists then, many groups would last longer than they do. But thing is that the girls never get close enough to a point where they'd wanna come to a pact like that. Instead the EGO of the girl or few who are singled out as potential solo acts by the management, label head, producers, etc. take it and run with it. Now that was Dawn in Danity Kane. It was Beyonce in DC (obv since her Dad was their manager).

...And if Beyonce was a true friend and equal member of DC she would have said when she was offered to singe most of the verses, hey I think Kelly/La Tavia/LeToya/Michelle would sound just as great as me singing this verse/lead on this song, I think we should hear her vocals for this part and then see.

BUT how many times do you seriosuly think that is said in girl groups, and especially in Destiny's Child and PCD?