Hmmm.
Greenbelt festival ticket prices for two adults and two children, tier 2 rate, bought in early summer = £510
Plus campervan/vehicle passes. Plus tent passes or tent rental. But we'll assume it's only the ticketed price rather than the additional £230-odd for a pre pitched tent plus parking.
Apparently, around 20,000 people attend. Let's assume that nobody goes top tier and that there are equal numbers of adults and children rather than the larger families often associated with some faith groups. It will probably balance out over the reduced prices for children, concessions with the later tier prices.
5000 families of four x £510 = £2,550,000.
Let us assume that she only managed to get 5% of gate. 5% of over two and a half million is £127,500. If she got 1%, that was £25,500.
She's either bullshitting big time or no wonder she's howling and wailing about not getting to go to festivals for the last couple of years.
There's one called the Stone Cold Sober Festival. £800 for that same 2+2 family. 100 camping spaces. £80,000. 5% of that if she were to be invited to speak about booze and drugs stuff, veganism or other such things that are firmly in her niche
when she's after some income = £4,000. Plus a free ticket, expenses, etc...