If I was in ISIS infested Syria right now and gave an interview to a british paper I would also not say strong words against ISIS, especially after joining them first, which would make me a traitor against murderous lunatics. Who knows if they're gonna find me and kill me. So I think we should take the unrepentant angle with a pinch of salt.
Bringing her back, especially considering she's pregnant, would be the right thing to do. Take care of the baby, trial her and try to rehabilitate her. She would obviously end up in some sort of national security watch list for the rest of her life. If she behaved, then it would be kind of a success story. If not, she would eventually contact other bad people and the secret services could even catch a few more bad apples.
Letting her and the baby there would send the message to others that there's no point trying to leave ISIS and I don't think that's a good message.