Difficult....very much depends on yours and her past history with food/eating/body image. If there is no history and weight and eating has been a non-topic until now, it's also very possible she just doesn't get enough food. Very hungry teenagers tend to eat a lot of crap because sugar and fat satisfy the hunger much faster than a nice salad. I'm an adult teenager myself and I still tend to eat the crap if there's nobody to spoonfeed me the healthy options. If the healthier options are available I will eat them instead of the junk but only if I've prepared them before the hunger hits.
First response would also be not to talk about it and make sure you don't buy junk food. You could however, if you think she will be ok with it, ask her if she gets enough food at mealtimes because you've seen her eat more junk and know this is usually a sign of being very hungry.
First response would also be not to talk about it and make sure you don't buy junk food. You could however, if you think she will be ok with it, ask her if she gets enough food at mealtimes because you've seen her eat more junk and know this is usually a sign of being very hungry.