Looking for a book

Glad you identified it

Found it thanks to google.
It’s the silence between breaths by Cath Staincliff.

Thanks but it is set in Britain

AI suggests it is The Paris Express by Emma Donoghue, it says:

The story features a young, radical anarchist named Madeleine "Mado" Pelletier who boards the train clutching a homemade bomb hidden inside her metal lunch pail (or bag). She enters the third-class carriage with the strict intention of detonating it before reaching Paris to make a political statement.

The Lives of the Passengers: The book is a multi-perspective look at the diverse lives of the people on board.

Hope this helps!