It's a sign of the times. Journalism today is reduced to vapid musings on short tweets from a source that is in all likelihood fictitious.  

Think about it! East Aleppo is under the desperate control of al Qaeda-affiliated groups that execute people for their beliefs and minor offences like blasphemy. Are they going to let a little girl freely send out tweets to the world? Tweets which could compromise their life-and-death struggle against the Syrian armed forces?

There are only two likely possibilities here. Either "Bana Alabed" was a fictitious propaganda ploy from the start, or her Twitter account has been co-opted by the terrorists that hold east Aleppo. If the latter, the terrorists may or may not have killed her for broadcasting to the world. The likelihood that the Twitter account bearing her name is just what it's purported to be is minute.