I'm sorry mate but being sent home early from sleep school twice is gold!! I'd be quite proud of that in a weird kind of way! Her determination will be a positive trait as an adult.

With the 'friend' thing, DS has only just started doing it. As in the last 3 weeks or so. He was given a puppy dog by a mate of mine and it was love at first sight He had a couple of 'friends' before that from when he was 6 months old because we were trying (futilely it seems now that I look back on his infancy) to create sleep associations. But now he has a major attachment to 'puppy dog' (they eat, sleep, play and do everything together, we even brush puppy dogs teeth before his I think it could be an age/developmental thing. And your DD is about 5 months younger than DS so a crazy attachment object could be just around the corner
The first time it happened I was devestated and cried most of the way home, lol! The second time I did have the weird proud feeling. They claimed they'd be able to remove our use for the sling and told me it was a sleep association that we could easily get rid of - within the day. Well when they finally gave up on her, they told me to put her in the sling as she clearly needed sleep and DD nodded off immediately and I walked out with the biggest smirk on my face.

Interesting what you just said about the 'friends addiction' - a few friends with slightly older kids have said the same thing so maybe it will happen soon. I keep on trying to force them on her, she has a fine selection to choose from! Fingers crossed!