I think we're overthinking the status of the player. Yes by definition this BR is now just a runner because she reached first. But if defense is attempting to tag this runner now that she has left 1B then the runners base path is from her location at the time of the tag attempt directly back to 1B with three feet each side of that direct line. She has NO basepath back to home. So if she runs away from a tag attempt towards home plate (as a runner rather than a batter-runner) she is still out. But it would be like running out of basepath anywhere else: it's a liv ball out rather than a form of INT when a batter-runner retreats.

We're still getting an out. There will not be a run down. :D

Thinking "out of the box". :cool:
But not a violation ;) :D :p

Yep, all this reestablishes is the force situation, not B/R status. For whatever reason, she could juke around back-and-forth, perhaps to advance another runner, but all defense has to is step on the bag.

That's how I would rule this. Once she reaches first base then retreats, she is no longer a BR, however she is still forced to go to first base as she can't occupy home plate, so the in order to get an out on a runner forced to advance the defense needs to only touch the bag.

It still brings up with the question of the base path should she get into a rundown between home and first however. I would agree since she has no path back to home she can't retreat back either.

I think we will definitely have an out and I would guess we would have someone very close to an ejection.

All of this because the coach "thought" and didn't actually observe the umpire's call of fair ball.

This is exactly what I tried to establish in my original reply. I will agree now after thinking about it that a "rundown" between 1b and home would be a live ball out as soon as she retreats to home more than three feet under duress of a tag, as her only legal path is to 1b.