Marshmallows For Breakfast by Dorothy Koomson
When Kendra Tamale returns to England from Australia she rents a room from Kyle, a divorced father of two, and begins a new job. She's looking forward to a fresh start and simple life.
Kyle's five-year-old twins, Summer and Jaxon, have other ideas and quickly adopt Kendra as their new mother - mainly because she lets them eat marshmallows for breakfast. Kendra eventually becomes a part of their lives, even though she's hiding a painful secret that makes her keep everyone - especially children - at arm's length.
Then Kendra bumps into the man who shares her awful secret, and things fall apart: she can't sleep, she can't eat, she's suspended from work, and the kids are taken away by their mother. The only way to fix things is to confess to the terrible mistake she made all those years ago. But that's something she swore never to do . . .