Ten is kinda of young. Yikes! Then again, I was 11 when I got mine, but I didn't start using them until I was in HS (about 14). Just tell her to be EXTRA careful!! My mom left a tampon inside her for about a week. She went to the DRs b/c she was having stomach pains and he pulled it out.
Thank God she didn't get TSS. She didn't use one after that, and she didn't want me to either. But, I did anyway.
Oh yeah, what if the string gets "lost" and she can't find it? Will she be okay at 10 with "searching" for it?