If what you mean by "a muse" is a very clear mental image of a character, that's one thing. But I've seen far too many people write about their muses as if they had an objective existence, not like a shorthand way of describing their own internal processes. This is especially true when they opine that a story has stalled because "the muses aren't talking." They're giving away their own agency when they do that.

But I will admit that I take issue (maybe more than I should) with alienating your own creativity. I'm a big believer in "one percent inspiration, 99 percent perspiration" as the recipe for creativity. If your story has ground to a halt, that's not a sign that the muses are uncooperative. It may be evidence that you need to rethink your plot, though.

Getting back to LKH, though, (and it is all about her, after all!) the failure/refusal to employ a series bible is telling. It means she doesn't believe it's necessary; if she really thought it was, she'd be doing it.