I don't know where you're getting this from. Beria raped a lot of women and girls and showed a very unhealthy interest in the daughters of several Party members, but even a predator like him was surely not stupid enough to rape Stalin's daughter while Stalin lived. Stalin did once fly into a panic after discovering that Svetlana had been alone with Beria in his home, but it's doubtful anything untoward happened. Even given Beria's power, there's no way Stalin wouldn't have skinned him alive, personally, if he'd raped Svetlana.