When she kills people in 3 hits that take a little over a second to fire, bringing silence is already too much. If you really think that winning against her is so easy as stacking your ENTIRE TEAM to harass her, why do you think that a drow picker forcing you to play, as a team, in a certain way is not broken? Does any other hero do that? Furthermore, the drow picker's team will expect you to constantly hound her, and they can easily play accordingly and set up counter ganks on you all day.
Forcing people to play a certain way just to remain in the game is something I consider broken. When your enemy is predictable they've already lost.
I guess next we can argue that SB is a bad hero because two stuns a huge movespeed aura and mapewide ganks at level 5 are so easy to counter. Having all 5 of your teammates grouped up roaming the map but still also farming is as easy as snapping your fingers in doters.
Every strategy you think you can come up with CAN be dealt with by Drow's team. The game is still 5v5, after all, and she will be even stronger than any other hypercarry at level 6 with a silence and twice the damage of a hero like AM.