Are you sure of that financial breakdown? Why didn't her management take care of the website etc, rather than paying her brother to do it?
Assuming those figures are correct, she would get a bit more than 20%. The tax would be deducted from her gross earnings, leaving 60%. Her management and Danny's fees would almost certainly be deducted from the net proceeds, not gross - in other words, 40% of that remaining 60%, leaving 36% of the gross sum for KP..
So if she earned £100,000 in a year, the Inland Revenue would get £40,000, management and Danny would share £24,000 and she'd get £36,000.