When I have lunch with my friend she can't stop looking at her phone and it feels so rude! How do I tell her I don't like this without sounding like I'm scolding her?

It feels like scolding because she's a grown up and really should know better, but our addiction to these devices is a tough nut to crack. And no one wants you to point out their bad behavior! It makes us feel defensive which doesn't mean you shouldn't say anything. You just need to tread lightly.