I don’t understand the logic to say that “men will anyways hear female singers” –
I assume we are discussing a frum singer who dresses tzniusdik. Why must she dress tzniusdik? People will anyways see immodesty!
Obviously, every person is responsible for themselves to behave tzniusdik in public. The same should seemingly apply to singing –
“קול באשה ערוה, שנאמר כי קולך ערב ומראך נאוה” (Brachos 24a).
The comparison between a CD and YouTube is ridiculous.
On the other hand, @lakewhut has a very important point: Jewish female singers can be a good influence for Jewish girls instead of the other shmutz on youtube.
Of course, like everything in the life of a frum Yid, every singer must consult her personal rov who can inspect the pros and cons and rule accordingly. I assume that they do so, and therefore there is really no need for us to tell them what to do.