I agree that it being messy works fairly good as a metaphor for the girls distorted lives, but I also think it was
overly messy at times, to the point several panels were really hard to parse. Doesn't matter how thematic something is, if you can't even see what it's meant to be.
Nah. They threw murder weapons into the water, to dispose of evidence. Aside from how they wouldn't do that if they planned to suicide anyway, there is also the fact that drowned bodies in very public waterways rarely disappear. Not to mention they had just gotten a load of cash and planned to eat croquettes. Or the fact that they wanted to deal with the belly first. Or that they just realized their love for each others and finally got rid of their issues, allowing them to finally have a happy future. and so on.
So no, they didn't suicide.