I'm loathe to dive into arguments that people have really strong feelings about, but I just wanted to bring up a point. Historically, high heels were worn by both men and women, both as a fashion statement and an aid to riding. The heels that Ciri is wearing aren't stillettos, just high, chunky heels. By point of comparison, if you look at the boots of pretty much any "Cavalier" from the English Civil War you'll see that Ciri's heels aren't that out of the realm of plausibility.
Cavaliers
Among my other historical recreations, I (as a male) have worn Cavalier boots with a three inch heel. I could ride, I could walk, I could run, and I could fence. And that's me wearing them on the occasional weekend. If I wore them day in and out for my whole life, I can only imagine it would be easier still. Regardless of the reason why CDPR put Ciri in high heels, it has a historical precedence and is not as limiting to maneuvering as one would think.