[Twilight spoiler!] I don't get the end...?

Question

"I'm betting on Alice," I mumbled.

And then the night closed over me.

Why does she say she is betting on Alice?

Answer 1

Bella wants Edward to turn her into a vampire. Edward refuses to so Bella wants Alice to do it. Alice also had a vision of Bella becoming a vampire.

Answer 2

she means that she thinks she will be a cullen (a vampire) one day :]  

Answer 3

Alice had a vision of Bella being a vampire. before in the book Edward says that he won't bet against Alice. So while Edward obviously wants Bella to stay human, and she wants to be one of them, Bella is reminding him that he shouldn't doubt what Alice sees. She thinks Alice is right about her becoming a vampire.

Answer 4

Because, Alice had a vision of Bella becoming a vampire and Edward doesn't want it to come true. So it's like, Edward is betting against Alice by saying it won't come true, but Bella is betting that Alice is correct and it will come true.