Update: 21st March I've now spoken to 3 sources who have read the scripts and each of them have said that in the scripts they have read the "because I love him" line does NOT exist. That's not to say it won't be said just that it's not in any of the early scripts. Be interesting to see if this line is actually said.
Update: 23:00 Here is another snippet from SuperFriendly.
I can tell you though that if episode 14 is as good as I have been hearing so far, it is going to be the best episode of LOST that you have ever seen. One of the most asked questions is actually answered in this episode. Like flat out answered, no ambiguities, no half-explanations, no things left unsaid: they just show you right there and then pretty HUGE stuff.
Source: SuperFriendly via DarkUFO
Here is a little snippet from a source called "SuperFriendly". I'm actively trying to find out if this is true but I've no reason currently not to believe it..... and shippers, please be nice in the comments :)
Also, during a scene for episode 14 Flocke tells someone: "I was waiting for you to change your mind". Now to turn the focus away from the important stuff, I can also tell you that Kate is talking to someone near the end of episode 14 and she says those words: "because I love him" refering to Jack or Sawyer, but the guy she is refering to does not hear her say it.
Namaste
SuperFriendly
Source: SuperFriendly via DarkUFO