It isn't that she 'only' did 6, it's just she didn't have any time to do more.
The first time she did London was Feb 26/27. She performed Liverpool on Feb 24 and Glasgow March 1. The second time she did London was May 30/31. She performed Birmingham on May 28 and Manchester on June 2. The third time she did London was Dec 16/17. She performed Madrid on Dec 12 and Paris on Dec 20. She just didn't have any time to add more dates