When Good Friends Go Bad by Ellie Campbell

All through school tomboy Jen, snobby Georgina, hippy Meg and gentle Rowan were inseparable. But when a childish prank turned bad their friendship was torn apart.
Twelve years later Rowan organised a reunion dinner and all did not go well.

Rowan never appeared; Georgina’s shocking secret was revealed; Meg behaved outrageously; and Jen finally decided it was time to move on. And that’s just what she did for the following ten years
Until now, when in the midst of her divorce Jen receives a desperate call from Meg. On a personal mission to track down Rowan, Meg manages to convince Georgina and Jen to put aside their differences and help her. But none of them even begin to imagine the extent to which their loyalties will be tested as their past finally catches up with them.