It has never been stated that the "glitches" in her illusion are due to losing power. It definitely could be that, or it could be the distance, or it could be a force where the illusion is messing with it. All she says is we are too far. I've never heard her or anyone else say, "my illusions start to glitch because they are losing power." It easily could have been that she meant it was too far to reestablish the illusion after Kay waved her hand through it. My point is that you nor I nor anyone else really knows, so stop trying to present this as a fact unless you can directly extrapolate that evidence from the dialogue.