As someone with an insulin pump, it tends to get low battery at the worst times. Also, you'll occasionally forget to replace the one you carry. It gets low every 1 or 2 months, so it isn't the most pressing matter.
I dont use a pump personally but i dont think she needs to carry batteries always. Going without insulin for a little bit isn't too life threatening unless you're going into DKA.
It's nice to know someone has your back, though
It's nice to know someone has your back, though