i just need a few things cleared up...

Well, yes. She did see it-that's why she was worried about Bella and didn't want to leave her alone. They tried to protect her but Bella knew that she needs just one moment they won't look at her and she will run away but it will be impossible for them to run fast because people will see them. Hope you understood me :)

but didnt bella make up her mind at the last segundo and Jasper was with her? if so Alice wouldent of got to her in time in a human speed.

hope this helps

I think Alice knew that Bella was thinking of running away, but she didn't know how - Bella didn't know how or when she'll make her move. Then, when she was far enough from Alice she fooled Jazz, went into the bathroom and just ran. If the sun wasn't up at that time, Jazz and Alice would've caught her, but they didn't. Hope it helped to clear things up :)