Copyrighted Dress Design

Small manufacture (women-home based) download a dress design photo (with dress model - face included) from a Facebook page (individual designer page - she has a boutique). Then she shared that pic in her whats-app group as her design demo (model face not blurred). Without knowing, a 19 old girl (one of her resellers) posted that pic on social media, owner of that pic found out that, now she wants to sue this 19yrs old girl and threat her thru the phone that she will sue her not for using her design instead using her model (model girl) picture without her permission. Sir, I won't know is this serious offense. that girl is really scared and her family is very poor, that manufacture playing anonymous she told her don't give any information, that designer asking for screens of that manufacture group (her design). There are many resellers working with this manufacture most is a housewife. but she is only threatening this 19yrs (sorry for my bad English)