I think the fact she's completely unrepentant kills any chance of forgiveness.
That's kind of where I stand on it, having done a bit more reading & thinking about it a bit. If she'd been found two years ago in a safe country/location & was wholly repentant and willing to accept she's made a mistake, then bringing her back wouldn't even be a discussion, as the overwhelming majority of people, myself included) would want to bring her back.
But the fact that's she's unrepentant until the end, no doubt waving that ISIS flag until the very last moment, and clearly still believing in the idea of what ISIS proposed? If she wasn't 9 months pregnant, it'd be a no brainer for me. I'd just leave her there, & if she tried to make it back (which she is entitled to do*), prosecute her to the fullest extent of the law.
But... She is 9 months pregnant, and she is a British citizen. All I hope for, moreso than anything else, whether she ends up back in the UK or not, is that her unborn child gets taken the feck away from her. Let a more balanced & normal human being raise the kid that's done absolutely nothing wrong.
*Like I said before, the fact that we're seemingly unlikely to put resources into "rescuing" her means we're very likely to see a GoFundMe campaign of some sort, giving her the necessary means to get back here on her own... Actually, has it started yet?