Here is a little example I noticed of how the slumber party experience informed Alice and Edward's interaction with Bella later.
Alice is very controlling, far more so than Edward; here is one more example of her playing dolls, with Bella as the doll and Esme's house as the doll's house. But the truth is that Bella likes being Alice's barbie doll more than she cares to admit. Alice's secret weapons are charm and sincerity of affection...plus the power to foresee exactly which games her victim will enjoy playing. She makes Bella the centre of attention, the very thing Bella systematically avoids and cringes from, but teaches Bella that it is a good thing to be loved and valued in your own right, that sometimes attention is a great pleasure."I have foreseen...," Alice began in an ominous tone.
Edward threw an elbow toward her ribs, which she neatly dodged.
"Fine," she grumbled. "Edward is making me do this. But I did foresee that you would be more difficult if I surprised you."
We were walking to the car after school, and I was completely clueless as to what she was talking about.
"In English?" I requested.
"Don't be a baby about this. No tantrums."
"Now I'm scared."
"So you're - I mean we're - having a graduation party. It's no big thing. Nothing to freak out over. But I saw that you would freak out if I tried to make it a surprise party" - she danced out of the way as Edward reached over to muss her hair - "and Edward said I had to tell you. But it's nothing. Promise."
I sighed heavily. "Is there any point in arguing?"
"None at all."
"Okay, Alice. I'll be there. And I'll hate every minute of it. Promise."
"That's the spirit!"
This is what we find in the slumber party; Bella is against the idea of being at the centre of attention yet the reality is not the horror she expected. The slumber party annoyed her, but she didn't hate it at all and part of her realises how much of it stems from the affection and anxiety her vampire associates cherish on her behalf.