Wilson, 35, will now ride Opposition Buzz in the equestrian events at Greenwich, where she will compete alongside William Fox Pitt, Zara Phillips, Tina Cook and Mary King in the three-day event team.
“It’s horrific and fabulous at the same time; I just don’t know what to say; I’m devastated for Piggy and wouldn’t wish this on anybody, she’s become a very close friend and I feel for her so much," said Wilson, who will appear at her first Olympics.
“What an emotional rollercoaster, obviously I’m so excited for myself and my support team but so saddened at the same time for it to be at the expense of such a good friend.
"To be thinking about London now is amazing though - having very much told myself it wouldn’t happen. We’ll definitely be ready."