Sabrina's Charley and Namus entries, for those (like me) who weren't familiar with the case. Both articles mention her hair being damaged by dye and the Charley summary indicates she might have had periods of malnutrition.
http://www.charleyproject.org/cases/a/allen_sabrina.html.
https://www.findthemissing.org/en/cases/8135/
The last time the mother was seen was right around the time Smurfette was killed; if they were trying to slip back into the US or fell in with the wrong man, they might both have been murdered. (Note: no, I am in no way suggesting Llorens could be Smurfette!)
On the theory that Sabrina might have grown up to look similar to her mother, I did a collage with Smurfette and Llorens. They do resemble each other somewhat -- and Llorens has quite an overbite that isn't that obvious on some of her photos.
I don't know how this could be followed up on, however. She doesn't have fingerprints and dentals would be meaningless for when she went missing. You'd think her family would have DNA.