If you are using Angular JS to send AJAX request and Cakephp isAjax function is not considering this request as AJAX then may be this can help you.
In you request add following header
headers:{'X-Requested-With':'XMLHttpRequest'}
Example
$http({method:'GET',url:'http://www.somedomain.com/',headers:{'X-Requested-With':'XMLHttpRequest'}}).success(function(data){ //Write your code here to handle response data }}]);