One more thing while thinking about Frankie - She had dark, curly hair. According to this article, so did Grace.
http://www.koamtv.com/story/14310951/a-southwest-missouri-cold-case-heats-up
Right age, weight, height, hair, general geograpghic location.... Frankie preferred to wear jeans, t-shirts and sneakers, just like Grace was found in.
But would Frankie have gone a year and a half without calling her family? Even though she was traveling across the country checking in infrequently, the last time she called her family was on Mother's day. Seems like she would have also called on Christmas or at least the following mother's day.
Here's a link to Namus for more pictures of Frankie.
https://www.findthemissing.org/cases/9595/0/