I think that Heather thinks she is 'helping Luke' by hiding the body. I think Luke is her obsession so she will do anything for him, no matter how misguided.
She is obviously adept at moving people around as no one noticed her hauling around a drugged Maggie.
So... As I suggested previously McBain is ALL about taking down Sonny via destroying Jason. Now that he has admitted it openly to Jason I am just waiting for the time that he slips up and tells someone (Anna?) that he gave Sam a fake vial of 'Franco" DNA. Or, maybe he will just have a nice long soliloquy on the docks. At any rate, once it comes out that he substituted Jason's blood for Franco's in the DNA sample then hopefully THAT part of the JaSAM journey will be over. However, there will still be the trust issue. Jason will still have issues with Sam over trusting McBain. How did he know for certain that "Teresa is Teresa"? Couldn't Sam be his half sister? Couldn't he have tracked down the wrong girl in Atlantic City and for whatever reason she said 'yes, it's me'. I hope so.
I love Elizabeth. I love her being Jason's 'friend'. I liked how Jason and Sam fit as people.
It has nothing to do with 'couple fans' or anything because frankly the couple fans on twitter are a rather virulent bunch. I just like how certain people 'click' and fit like I imagine a 'real couple' would.