The sentence I'm talking about (in bold), along with relevant context:
She was eight years old and small for her age, and the baby brother she carried on her left hip was large and plump [...] He was holding a biscuit in one hand and a bright red plastic spoon in the other; while the top part of his little body was well protected by a vest, shirt, coat and an over-sized bib, the bottom part was bare. Round the ankle of one leg was a little silver anklet with two bells.
[...] The little silver jet that arched and fell to the ground delighted the baby, who made an attempt to touch it, and the girl, who had been scolded by her mother on several occasions for not taking care of her baby brother so that he sat in his own puddle and splashed in it, now said sternly "Tee Tee, you dirty boy, leave it alone!".
— "Big Sister" in Or Else, the Lightning God
The sentence seems unnecessarily long and convulated to me. Too much information crammed into one single sentence. But I more or less understand the gist of it. Still, it would certainly be helpful if someone could break it down or simplify it.
What I'm not sure about is what "little silver jet" and "his own puddle" mean in this context and how they relate to each other. My overall understanding of the sentence (that is, what the writer is actually trying to say) is hazy at best. I suspect there's some baby vocabulary involved. Maybe words like only mothers or grown-ups use—which I'm naturally not very familiar with, being only 13.