Gossip Girl episode 3

Chuck discovers that Serena has been going to a rehab center called Ostroff and he  thinks that she is the one in rehab because of drugs. But the truth is that Eric, Serena's brother, is the one who is in rehab because he tried to kill himself cause he had depression. Chuck tells to Blair about what he thinks and in front of all the Ivy League says that Serena was in rehab but that for now she is sober. She humiliated Serena but then Eric tells to Blair the truth and she feels really bad about what she has done.
In the end Blair goes with Serena and they talk and forgive each other. They are friends again..