Just a random thought...
....But, we all know the beach scene where the compass points to Jack and then Liz gets all upset and says it doesnt work....
Well i was just thinking....Will came from the same direction the compass was pointing. So although i htink Jack/Liz have the most perfect relationship ever! Its possible that the compass could have been pointing to him at that moment....Cuz if you htink about it even thought Liz TRULY wants Jack, she was upset cuz her mind was telling her not to. She needed Will there to see who it was she REALLY TRULY wanted....she needed to do like a test or sumthing like that. So she wanted Will there at that moment so she could prove who she wanted.
So im not saying that i htink she wanted Will at that moment because she loved him, im saying she wnated him there so she could prove she didnt want Jack (which she was proved wrong after the kiss)
^^sry i know all that was confusing....