Three former employees of a graduate school in Essex County have plead guilty to a $1.3 million scheme to defraud the university, in a scheme that included asking vendors to pay them directly, purchasing hundreds of thousands dollars worth of gift cards and forming a shell company to bill the university for services never rendered, U.S. District Attorney Philip R. Sellinger announced Friday. Teresina DeAlmeida, 59, of Warren and Rose Martins, 44, of East Hanover pleaded guilty to wire fraud conspiracy in Newark federal court Friday. Silvia Cardoso, 61, of Warren, pleaded guilty to the same cha…