Could have said the same when they made CJ the main character in San Andreas. I'm sure if that came out now, people would moan about that too and say it was pandering. It's a game about criminals, there are obviously female criminals, so I wouldn't call the change "unnecessary".
Also, the female character will be just one of the main leads, so it provides room for new angles, IMO. Mixes it up a bit. What I liked about the last one was that there were 3 characters with 3 completely different backgrounds, so it allowed you to see into their completely different lives.