Um, no this is not acceptable. You do not retaliate in this manner for the reasons you stated, they may be going through something and you have no idea what that might be.
I'm with you. I've watched girl drama for years at school, and retaliation never leads to anything good. The girls that are most successful walk away from the drama with their own circle of friends. They politely refuse to be the ping-pong ball between the queen bees and cultivate friends and interests elsewhere. It's not always easy, but it beats being in the middle of the drama.