Is it illegal for photographers to post pictures of you without your permission on their sites?

My ignorant redneck brother in law and his fiance are in a feud with a local photographer (one of those "businesses" where someone chooses a name and then charges for mediocre pictures). His fiance took a picture off of the photographer's FB where she displays her recent works for the families to preview the pictures before choosing a package to purchase. She edited it to display her children's names and turned it black and white. The photographers assistant asked her if she did this and asked when she'd be purchasing a package seeing as what she did was copyright infringement without doing such. My sister in law replied saying she didn't change it (it was very obvious she completely did) and that its her FB and she's adult and can do what she wants. The poor photographer put a post up later reminding all her clients that copying, pasting, and editing photos off her page is illegal unless purchased. My sister in law wrote on it saying "and with this being said you also need to know that it is illegal to advertise our family photes to other people that should be private. if you where professional you would no that you need to remove my family photoes from your page." Yes, I know she sounds completely stupid. Anyway I was just wondering if what she is saying has some truth to it? Also, the pictures taken were actually for her cousin and grandparents and they were just able to sit in on it. She claims she shouldn't have to purchase a package when she only liked one picture.