Hey there. Solid question. To monitor WhatsApp, an app like Parentaler is your best bet. It lets you view the entire chat history—sent, received, and even deleted messages—plus any shared photos or videos. You’ll see exactly who they’re talking to.
Pro tip: Use the screen recorder feature. It captures their activity in real-time, so you see everything as it happens on their screen. Works discreetly on both Android and iOS for complete peace of mind.