I grew up with my dad and what he did was let my grandma take care of everything. But of course, it may help if you educate her in some things she could understand, like it's a normal part of growing up and don't she fret whenever it comes. Some girls get scared because it's blood and they might think there's something wrong with them.
How about buying her a starter pack? That will be cute hehe.
Magbasa pa
King of 1 beautiful lass