Your grandmother isn't entirely wrong, but it's not the miracle cure you see all over social media 😅 Dandelion has compounds that studies have linked to liver-protective properties (basically they could help your liver work better), but we're talking about modest effects. The reality is your liver already detoxifies itself just fine if it's healthy - that's literally its job. Tea isn't going to "cleanse" anything magically, but it can have general benefits if you drink it every now and then.
Where people mess up is with the word "detox." That's pure marketing. Your body doesn't accumulate toxins like a dirty air filter that needs a reset. If your liver and kidneys work normally, you don't need to detoxify. That said, dandelion tea probably won't hurt you (unless you're on certain medications), so if you like drinking it, go for it. But don't do it thinking it's cleaning or fixing things - it's more like a tea with a few compounds that could have subtle effects. Your grandmother's been doing fine for years probably because she takes care of her health in general, not just because of the tea 🏕️