1. Why do you think Bella doesn't want to go to the spring dance? She could easily just have said to anyone, "Let's just go as friends". Why is it that from day one, none of the boys appealed to her?
As Twilight is written in the first person, and we are given no reason to distrust Bella's POV, I believed what she told us - that she was too clumsy to go to the dance, and that she didn't want to upset Jessica by saying yes to Mike.
Bella has already described Mike as 'being like a Labrador', and imagining him 'with a wagging tail', so although she obviously likes him, she doesn't like him in that way.
The others - Tyler and Eric, never seem to catch her attention much. Tyler just annoys her with his constant apologies over the accident, and Eric never really seems to register on her radar. I think that having been 'ignored' by the boys back in Phoenix, she just wasn't used to getting attention, and as shy as she is, she doesn't like it when she does get that attention. And then her draw to Edward, her 'incoherency' when she's around him, his 'beauty', all take up her attention, leaving no room for the others.
From Midnight Sun, we learn that it was the same for Jessica (sort of) - she had a major 'crush' on Edward, and only went back to Mike when it was obvious Edward wasn't interested. Lucky for Bella, he was interested in her, or she may have had to 'move on' as well.
2. Bella asks Edward if he has multiple personality disorder because he either seems to be overly friendly or sarcastic moments apart. To what did you attribute Edward's odd behavior?
His being a vampire. I knew before reading that this was the case, and that he and Bella were going to end up together. I imagined that his friendly moments were when he was enjoying the moment, that he liked/fancied Bella and was being his 17-year-old self. When he turned sarcastic, I assumed that he was 'remembering' (as if he could forget, but you know what I mean) that he was a vampire, that he was a threat to this girl. And his warnings, or threats, seemed to fit in with this - he wanted to get to know Bella, but knew it was best for her if she didn't. I also assumed, after their first meeting, that he must be thirsting for her, but trying to overcome this.