Could be different Father for her and Gary, Nelson could be her 2nd marriage and Habeck her third married name? Hard to say but given the circumstances there may be blended family drama or police that refused to take the missing person report if they did call originally.
Additionally in Jefferson County Charlotte went missing just 1 month prior (June 1974) another girl Catherine Lynne Sjoberg
The National Missing and Unidentified Persons System (NamUs) went missing from the Concord house (in Jefferson Co)
The same Concord house where Edwards abducted and killed 2 in 1980