Abbott could be technically correct, however. The ECHR was set up by us at the end of WWII and the treaty we signed up to stipulated no nation could make someone stateless. I realise they're trying to say she has Bangladeshi citizenship through her mother but it's far from clear cut. And refusing her re-entry could create a lot of unrest among the Tower Hamlets Muslim population.
As a side issue, those who voted Brexit to cut down immigration never bothered to find out that most of our immigration comes from India and Pakistan. But then, they never let the facts get in the way of a good argument.