Cat and the Stinkwater War by Kate Saunders
At first glance there's nothing special about the white stone which Cat's archeologist father gives her. And all his stories about Ancient Egypt and mysterious cat gods sound totally daft. But then Cat makes an incredible discovery. The stone DOES have amazing powers. Power to make her graceful and beautiful. Power to defeat bullying Emily Baines. Power to turn her into a CAT! But all is not well in the feline world around her, for the Blessed Sardine - the cats' holy relic - has gone missing, plunging the rival dynasties of the Cockledusters and the Stinkwaters into all-out war. Now only one small cat - called CAT - can help!