or have the woman lying dead next to you the following morning
then a pop up : quest failed :)

Except that he game always makes meditating/sleeping safe. Just make it to the campfire. So, I think that this was an intended, puzzle solving type solution intended by CDPR, rather than the more actiony fighting your way to safety solution.

Not always, you can die before the screen turns black, when the camera starts tu turn on and on... You can die.

Maybe. Never had it happen.

or, just take the river road. only 1 (maybe 2) Barghest packs spawn, and then you're fighting drowners until you get to the outskirts.
sure, it's a bit longer, but much safer.

She's very good at finishing off stunned drowners for you, too. But she will complain that you're not going the right way.

If you use the "spend the night at the campfire" workaround, you can end up with her both at home and at the inn at the same time :)

If you want to do the barmaid quest the "right" way, the most important thing to remember is to do it BEFORE you get the quest to light all the fires for the Reverend. While that quest is active, even if you've already lit the fires, you'll get double spawns of barghests along the road. By postponing the main quest until the next day, you'll never be fighting more than 2-3 barghests at once, which makes keeping her alive MUCH easier.

Or you could take the lakeside route, of course.