I don't think it's boringness, but the biochemical rush of having a drama that drama-queens crave. It does sometimes seem that way. I had a long conversation about personality disorders just the other day - those grey areas of mental health dysfunction - and I believe that the constant drama-making is a feature of one or two of the recognised ones. Often the person has a way of viewing the world that is triggered by certain events - it might something like fear of abandonment, or need to control the people around them in order to feel emotionally secure.
Having a drama to generate attention is a skill we all possess, I'm sure (think of your average 2 year old, and we've all been 2 before LOL). It's a question of what the payoff is. For example, if I as an adult have a tantrum about something, I have to deal with the embarrassment of it, so I'm inclined to NOT have those sorts of dramas, by using other skills to get what i need. But if I haven't yet developed those skills, or have always been rewarded with attention, getting my way, manipulating people who comply in order to avoid the drama etc, then the payoff is much greater, and i"m less likely to resort to a more mature toolkit for getting my needs met.
Don't forget though that your DSD's friend *is* a teenager, and the row was with her mother, so it may well be something developmentally normally like seeking to establish her autonomy - she could be more moody at this age and then mellow as she grows. The drama she's experiencing is utterly real to her - which makes it harder to deal with. I'm sure having a friend like your DSD who can acknowledge how she's feeling and at the same time re-frame the events to give a different more balanced perspective is very good for her. Eventually tho DSD is gonna have to decide how much 'work' she's prepared to put into the friendship, and whether she's getting a return for her efforts.
ETA Kaz - I didn't read your post before I posted, but we're on the same page!! LOL
Bookmarks