Stock the kit. There are a number of things you should put in the kit. These items will prepare her for most scenarios and most emergencies. Hopefully, it will give both you and your daughter the peace of mind that she'll be prepared when the time comes.
2 Pantiliners
2 Pads (add more, if you don't use tampons).
2 Tampons in different sizes (add more, if you don't use pads).
Midol or Ibuprofen for cramps.
Hand sanitizer. Explain that she should wash her hands and use soap or use sanitizer before and after taking off and applying a pad or tampon.
A small pack of tissues. If there is a shortage of toilet paper or she needs to be more discrete.
An extra pair of panties and pants. Just in case.
A mini garbage bag or ziplock bag. If she doesn’t have access to garbage, she can put her used supplies in a plastic bag and dispose of them later.
A small pack of wipes. Wipes are much more durable than toilet paper, but be sure to tell your daughter not to flush them down the toilet.