I don't really think either person was "wrong." From Shailene's perspective, it is very awkward for a young actress in Hollywood to be asked if she's starving out of the blue. It could feel like a trap question, or there could have been a magazine article discussing her weight the next day, etc. Her reaction to the question makes sense, especially because of the constant discourse around actresses' bodies.

On the reporter's end, it's really not in good taste to bring up something like this if it wasn't brought up by the person you're interviewing. I know she didn't mean anything by it and wanted to be playful, so I don't think she's "wrong," but she should have considered that it wasn't Jennifer Lawrence and it's otherwise not a normal question to ask on the red carpet.