Mainly the last part with Dulaney or whatever her name was.
Still, not proving a source for the fibers doesn't prove much. It provides a possible link between DW and Danielle. There has already been an admitted link, (GS cookie sales) and a possible link (MH in the park, Danielle allowed to go to park by herself).
So, undeniable proof does not exist in this case What does exist?.
(1)Danielle is dead.
(2)Someone did it.
(3) Police need to find out who that was.
(4)It obviously wasn't DW.