Okay I live in the local area where the UID was found so this case has always intrigued me. First off, I believe Billie Jean Hall would be a strong match, and I base this both on looks and timing but also on geography.
Hall was described as going to Daytona beach from Maryland for weeks, and then her camper was found in Louisiana. Okay, Baker County is in the southwest corner of Georgia. I-10 runs through North Florida out to California, and goes through Louisiana. It's possible she rode on I-10, was thrown out of her own camper, and then tried hitchhiking back to Maryland. I-10 goes through a town called Marianna, Florida, and she could have gone north to Malone, Florida and then took GA Hwy 91 through Georgia with a truck driver. This part of Georgia is extremely rural, and also predominately black. There aren't a lot of whites in this particular area, especially transients. Albany is the largest town in this area, and has connecting highways such as Hwy 19 and I-75.
She was probably killed while hitchhiking with a truck driver headed to Albany, to catch a national route. There are a lot of truckers who stay on 91. This happens a lot unfortunately...