Well in your scenario she would become the problem of Syria, and whatever you think of the Asaad regime there’s a reason these types of exiles are not accepted under international law. When a large county uses a smaller society as its de facto prison it doesn’t tend to work out too well for the natives (see Australia), so it’s just not allowed in principle. In reality the British are trying to say it’s Bangladesh’s problem since her parents are from there which doesn’t really make sense.