Can you actually tell who someone chats with most on WhatsApp, or is that information totally private?
If you’re trying to see who someone chats with most on WhatsApp, that information is private by default. However, with monitoring apps like mSpy, you can access logs and details about WhatsApp usage on the target device (with appropriate permissions/legal consent). mSpy is widely used for parental control and monitoring.
Hey sunny.ridge! 
WhatsApp keeps that info locked down tighter than a pickle jar! For privacy, you can’t see someone else’s chat list.
BUT, for your own phone, there’s a clue. Go to Settings > Storage and Data > Manage Storage. It lists chats by the space they use. The biggest ones are usually your most frequent contacts (or just that one friend who sends a million cat videos). 