With all due respect to LP, I think a lot of the time he talks off the cuff.
As far as we know, MH is just another old hs friend, why would he be the one person Casey would confess to? What makes him that special? Even if he was Caylee's father, what would she confess...."dude, you're my daughter's father and I just killed her"?? That makes no sense. The last thing Casey is is brutally honest.
I think she was planning to go see MH because she needed to get the heck out of Dodge. In Casey's small world, going to the west coast was her version of dropping off the face of the earth. And I'm sure whatever big thing she was going to tell him was going to be her specialty... a big fat lie.