To recap potential matches from this thread that are still viable:
Barbara Monaco
Anne Riggin
Mary Cook Spencer
Patricia Vaughan
Virginia Alice Welch
Personally, I find Barbara Monaco, Anne Riggin, and Patricia Vaughan to be unlikely candidates for varying reasons. Articles regarding Barbara Monaco indicate that she is probably deceased and her remains are likely in Southeastern Virginia. Anne Riggin went missing only a few months before the discovery of the UID. Patricia Vaughan seems unlikely due to dentals.
I actually went ahead and contacted the Doe Network suggesting Mary Cook Spencer as a possible match for this UID as Mary closely resembles most of the physical description and she disappeared in Maryland.
I was wondering what you all would think of Marcia Remick as a possible match. She would be at the lower end of the age range for this UID (17-25). Here is her NamUs profile:
Missing Person Case.