I got off of work around 5:30, went home to pick up the bag of fluids and headed to the ex's house to give Toula fluids to make her more comfortable. When I was nearly there, he called and said that Toula had died in her box on the porch.
While I feel awful about this, it seems to have been fairly painless; she only stopped eating last night (ate normally yesterday) and got to die in her box at her own home.