You makes your choices in life, then you reap the rewards of your actions.
Shamima Begum chose the jihadi path when she left the UK to join Islamic State. She was not ignorant of the world view on terrorism, yet she still went ahead.
Now she wants to come back to the UK, to fight for her citizenship. Citizenship of the country, on which she turned her back.
BBC News – Shamima Begum cannot return to UK, Supreme Court rules https://www.bbc.co.uk/news/uk-56209007
The Supreme Court have made the right decision, confirming that Begum should not be allowed back to the UK, to fight for British citizenship.