Two sisters, one a youngish teenager and her little sibling who's a toddler. Their mum disappears (can't remember exactly what, I think she just doesn't come back one day?) so they leave where they're living and become homeless.
The bigger sister tries to look after her little sister, finding them safe places to sleep etc, finding food.
I think at one point they sleep on a beach? And I feel like the big sister's name began with D but not 100%.
I'd love to know what it was called and read it again.