I was pretty sure she left voluntary with the Walkie Talkie dude.
You can see Lee placing the Walkie Talkie on the table and falling asleep.
Plus Clementine REALLY wants to find her parents. It's her top priority. And she thinks that guy knows where they are.
And Lee obviously can't provide this. Just before that Clementine asks again about finding her parents. And no matter what you choose she will know that you won't go look for her parents and starts crying. So yes, I am pretty sure she left voluntary to the creepy dude hoping to find her parents.