Distinct possibility Curly - however it gets hard on those around them.

My DD's friend seemed to get more and more possessive no matter how much reassurance she received.
I totally agree. It is extremely wearing being around people who think that if they can get people to feel sorry for them that it will get them love. People like this need to be sat down and gently told that their approach isn't getting them what they want because it can years, even decades, to figure it out.

I'd say the mother of your DD's friend is aware, at least on some level, of how unpopular her daughter feels which was why she contacted you to try and salvage the friendship. What an uncomfortable position for both of you to be in

As you may have guessed I have some personal experience in this area with people like this but not going into details because I think I am being cyber-stalked.