Ok, so I have been asked why Bella wanted to become a vampire. And my answer was that she was positive that she wanted to spend the rest of her life with Edward, that she couldn't live without him. She was so fixed into thinking about wanting to turn into a vampire like her partner. within being with Edward for a couple of months, she was so fixated into being a vampire, that she had her full trust in Edward to turn her into a vampire. This topic is kinda tricky to answer actually becasue nearly everyone knows the answer, you dont have to be stupid to know it, it's just logic.