Daniela Rausnitz, who had a torrid affair with married investment banker David Gray, 28, sent him steamy messages just days before she sicced London cops on him, according to testimony in the case. “There were countless texts and e-mails in early August of a very affectionate nature,” said Gray’s London attorney, Dan O’Callaghan yesterday. O’Callaghan and Gray’s mother said the number-crunching nerd simply lost his mind after his colleague at JPMorgan Chase dumped him for another guy, deluging her with hundreds of e-mails. [NYP, earlier]