Tracey, we remember, has, in her past, fallen to the ground. Everything that has happened in the recent past has bowed on top of her, through her; the burden of it has been too much to bear and she has buckled, weeping uncontrollably, to the floor. The weight of all that has happened, the crushing confusion she is experiencing, its pain, all contributing to her mental and physical disintegration.
It's as if her body is a building upon which her time has rapidly speeded up. Bit by bit, then swiftly, structural integrity is undermined, then finally destroyed. It has collapsed.