CC Dress have double collar bone..

Hey I'm not sure where should I put this but there is the issue that's been bothering me.. I've downloaded a CC dress and it give me this wired double collar bone effect.. I don't think it is a CC skin problem because non of my other CC have this problem.



I have found this post : sims4studio.com/thread/9643/sharp-line-on-collarbone here that seems to be having the same problem.. but I really have no idea how to fix that even with his example, can somebody help me please?

This mesh is not created by me and I do not intend on posting the fix .package anywhere, it is purely for my own gaming use because this is driving me crazy...


so I went in Blender and took a look, pulled up a EA mesh for comparison and Think MAYBE this is the case...

This is the EA mesh , the chest and collar area is without overlapping,
 

This is the CC's mesh

clearly there is overlapping happening on the chest area...


But I have no idea how to fix it..
is there a way for me to take the EA's mesh section and paste onto the CC's mesh?

I've tried the shift+d and P, but for some reason it is not working for me. Those hotkey do not register, so I used the menu option  under Mesh-Add duplicate, but that only allows me to move that piece of mesh within that project, it is not letting to to paste onto the CC project...