She's gonna die with all these vitamins she's taking.

I don't know exactly what vitamins she's taking, but if she's taking in essential vitamins, which are fat-soluble, then it could be doing way more harm than good. They are stored in body fat and taking them in excess can cause them to build up to toxic levels.

Taking vitamin supplements are only necessary if you have a deficiency in something. Like me having Sickle Cell I have to take folic acid and iron. Otherwise, it's recommended you get your daily dosage of vitamins from a balanced diet which I'm sure Katy has a pretty strict one.

It's common sense. Too much of anything can be bad for you.

Ironically, she's kind of a mess.

Vitamins & supplements can do more harm than good.

I just noticed the lyrics in one of the songs on Prism, "This Moment"

She only takes one of the small packets in the bag (the big bags divide the small packets for breakfast, lunch, dinner).

Lots of people do this, it's not a big deal. Considering most are probably B and C vitamins (which aren't even fat soluble, so most of any extra isn't even absorbed) and antioxidants, it's unlikely to do much. I would presume she's able to afford high quality supplements.