Previous instances have seen sentences differ wildly depending upon a number of charges related to the offence, such as financing Terror and social media posts. Around 2 years seems standard..I think you are correct in that on balance, she doesn't seem to pose a risk to the UK, but the risk to her and her child are high.I think that what people are concerned about is that their maybe insufficient evidence to convict her of more serious crimes under existing anti-terrorist legislation. Lack of eye witness evidence, lack of hard intel etc...
So she is guilty of belonginging to a terrorist organisation that much we could prove - so if she ever did return to this country, she could very well be tried and convicted of that although I'm not sure of what type of sentence she would be given. This would probably be followed up with many years of a probationary monitoring system being put in place (has to report to police station 3 times daily/nightly curfew, blah blah). All running alongside some form of rehabilitation / de-toxification process.
Personally I don't think she herself presents a threat to the British public, however she could be seen and used by shadier figures as a figurehead, a living, rallying symbol of western oppression against Islam. So in that sense she does still pose a security risk and that needs to be taken into consideration.
Don't know what the answer is here. I hope that we don't let her back. I don't care where she ends up beit Bangladesh, Amsterdam or rotting in Syria.
There's hundreds more just like her in Syria being held by Kurds/US/Syrians and they will want to come home as well. What do we do then?
You have to add in the fact that she was 15 at the time as well.