does the color match her sheets pillowcase sweater she wears or anything like that? tell her clarifying shampoos are not non residue in fact they leave residue themselves but they are very harsh and highly toxic (within what the law allows..barely) they are meant to strip heavy buildup..like that.. (so obviously isn't working) they are meant only to be used about once every 4 months at most
this looks like lint from a hat swater or t shirt..maybe
could also be from living in a city, the air in a city has tire rubber burnt oil and all sorts of other gunk that leaves a thick black gunk on your skin in your hair..and if you go barefoot for just 1 block you get black feet
you said you helped her clean her hair...why? this to me is an indication she doesn't do it herself very often?
my recommendation
www.dreadlockshampoo.com makes a charcoal 'detox' deep cleanse. its not on the site just order any other bar and request a substitution
also get any other bar or liquid (liquid if young bar if mature they look young though) after using detox once or twice wash with the other every few days
if theres a scent... get rot knot
otherwise try to match the color with anything cloth or wool she sleeps on sits on or wears regularly, if need be replace it or cover with a microfiber silk or satin cover
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My new book Ban The Taboo Vol 1