His Other Lover by Lucy Dawson
Mia thinks of herself as a grown up. Her twenty-two-year-old sister, Clare, is once again in the death throes of an affair that was always doomed to failure. Mia now understands that relationships need work; that in an adult partnership, passion and spontaneity give way to something different but more lasting. With Pete she knows that her search for 'The One' can stop.
Until, tripping over Pete's phone on the way to the loo one night, she reads a text message that sends her blood cold. Everything in it - its tone, the kisses at the end, Pete's evasions about the sender 'Liz' - is wrong, and suddenly the blinkers are off. It's time to get back in the game, and with everything to play for, Mia is about to discover a capacity for deceit she never knew she had. After all, when Happy Ever After is at stake, any weapon at your disposal is fair game - isn't it?