Her father did say she had a more adventurous side and and this appears to have continued into her adult life. If she was interested in a particular type of man a personal ad would target that particular type. If she exploring a specific sexual group she would be placing ads in publications aimed at those types.
She was known to use the public phone box which must have been out of choice as she did have a mobile phone. If she had placed an ad under a PO box number she could access the replies to those ads by the public phone choosing to whom she wanted to reply to without giving her personal mble number publicly.
This may explain the two asian men seen at her door, and the man with rucksack on his mble also seen entering her door.
Did she place these ads by letter.. Is the letter she is seen posting a personal ad