What a girl gets when during the night when she's wearing a pad and gets blood all over her fingers during the night. This is caused because she unconciously touches her vulva/masturbates in her sleep, because her fingers so naturally move down there, and anyways, she's more horny when on her period. So, her fingers are covered in red and the blood gets down below the nails, and she finds this when she wakes up.
Yeah, I get period fingers every night when I'm on my period, unless I wear jeans or something to bed, so I can't easily get down there. When it's just PJs or undies... yep, I get period fingers. Hate that.