Here's further info on litter training:
https://rabbitsindoors.weebly.com/litter-training.html
As for what to do when she goes in the wrong spot...I'd say ignore it. Putting her back in her cage as punishment doesn't really work for rabbits. It only succeeds in making her cage a place she does not want to be. That wouldn't be beneficial for her or you. Rabbits aren't going to be "trained" to please. They don't respond the way dogs do -- dogs
desire to please their human. Rabbits do their own thing.
We don't really "train" rabbits to potty somewhere. They choose
where to potty. We just have to capitalize on that and create a space that will attract them (ie. a pleasant litter box they want to be in). When they have a litter box that is enticing, they choose to go in there. Once they've established that as their place to go, they tend to stick to it.
In your case, it's a matter of ensuring the original box is more enticing than the corner. That means removing the odor for starters. If her current box isn't filled with hay, try that to entice her. If it doesn't work, put a litter box in the spot she's chosen.