I have this chat with the grade 5/6 girls at school quite often.
One thing that often comes up is the smell. And I remember quite clearly being horrified at the smell- never having had experienced before I was disgusted to think others may be able to smell it and I remember constantly sorting vanilla air fresher all through my bedroom and going overboard on the vanilla kisses impulse. (To this day I hate the smell of vanilla!) she may find comfort in the fact that 90% of the time no one else can smell it, and the other 10% is when it's really strong because she has left it too late to change her pad or tampon.
Another thing I always tell young girls is if they find themselves with heavy periods, they might want to ask for some new underwear, and start using their old underwear during their period only. That way they will still have nice undies 3/4 of the time that won't be stained etc.
at the end of the day of there is a stain, the best thing to do is to put the undies straight into a bucket of water with some napisan until the next wash. Just a few practical things that I always felt helped.