Never one to object to the cruciatus, Bellatrix smiled and watched as Remus suffered under Sirius's curse. Even if he refused to scream for them, the sight of him suffering still spoke to some dark and twisted part inside of her.
Not that she was going to tolerate his silence.
"It is so much more satisfying to break the stubborn ones," she mused as she lifted her wand and cast a silent cruciatus of her own at Remus, gesturing for Sirius to do the same. Perhaps he could withstand one without breaking, but two? Including her own? She was highly doubtful.