She slept until, a fire burned.

Well, I see now, but...

It almost seems as if you're being a little too clever here.
Likely, the vast majority of people won't see this; they'll
simply be scratching their heads over a sentence that
won't parse.

I agree.  Sentence just doesn't make sense with a pause there.  Try speaking
it out loud with the pause there and see how it sounds.  To the vast
majority of people it sounds extremely unnatural.

You are, of course, allowed artistic license.  Heck, e.e. cummings broke a
lot of the rules of traditional poetry, and he did all right.  If the comma
means so much to you, go for it; I'll support you.  But be prepared for
99.9% of the people who read this sentence to look at you with a puzzled
expression and believe that you don't know anything about grammar.  :)

-Richard