Give over. Half the people on this thread are inferring she has diminished responsibility. There's a thirst to get her back in the UK and give her a ticking off, at most. It's absolutely clear as day, and anyone with half a brain cell can see it. It doesn't matter if someone says openly 'let her off', or makes it out using a variety of semantics. Most people aren't stupid. The rage isn't about the justice system, it's about being on the losing side of the decision. There are some people (many found on this off topic chat), who are so soft they hide behind pretending to be 'compassionate', and in the process think they can take the side of an evil piece of shit unchallenged.
Shimima Begum joined a terrorist organisation. If you want to play being compassionate, have a think about those poor blokes in orange jump suits on their knees, about to have their heads cut off. Many of which were volunteers trying to help others. She was complicit in that.
Even when I have said that should she have been 18, there would have been another excuse, my immediate post was met with... Another excuse: 'She might start a new terrorist movement'. Well, five minutes ago you were pleading that she was showing remorse, and we should let her back in. Which is it then? No answer obviously, because it is just any excuse you can grab, the age being the current most convenient one.
The authorities have made their decision, and it is absolutely the correct one. Shame on you.