Tbh there are a lot of weird pauses in DoC. In the scene where Lucrecia and Vincent meet, they just stand there and stare politely at each other for a full ten seconds while kindly waiting for the fade-in and camera pans.
https://www.youtube.com/watch?v=oQaMDeVM-Ns
Likewise, Vincent and Rosso do a lot of polite standing around and waiting for cameras to pan and transformations to happen in this scene in which one might otherwise assume urgency to be appropriate:
http://youtu.be/X_mQ6ElM7qs?t=3m40s
(My favorite is when Rosso pulls her fist back to strike and then kindly waits about 4 seconds for Yuffie to run into the room and interrupt her.)
and the final question, in the final scene in the seven heaven, shelke say:
Shelke: Vincent.
Shelke: Do you remember the last words we exchanged?
Shelke: Do you remember our promise? Your promise to Lucrecia?
Shelke: Go. Tell her how you feel. Tell her what is truly in your heart.
Shelke: I know that you probably will never see this but I have to try... I have to believe.
[She places her phone down, as we see a text message is being sent. Cut to outside the Seventh Heaven, where she sits, with a yawning Red XIII by her side (yes that's the first time we've seen him in the entire game!)]
Shelke: I've learned I must never give up hope. Never...
And she have a cellphone in her hands, and then she put the mobile in the table, and say: I know that you probably will never see this but I have to try... I have to believe.
what was the meaning?
...It means she was sending a text message to Vincent that said what she was narrating to us, and she's only sending it on faith that he's still alive out there somewhere and will be able to receive it.
As for the "promise" and "tell her what is truly in your heart," the only thing resembling a promise like this is when Vincent says something to Shelke like, "She was always like that...only believing what she wanted to," and Shelke says, "Vincent, don't you think should tell her that yourself?"
Which, you know, has nothing much to do with him saying, "Thank you. It was you. You were the reason I survived," unless you want to consider that to be a loosely paraphrased "I love you," but it would hardly be the first bit of dialogue that makes no sense.