I’d happily employ someone who had the guts to do all of that, success or fail, that’s a mountain of experience to apply going forward.
Anyone who couldn’t see that is someone you probably don’t want to work for, so I don’t think unemployable is fair.
The more interesting story to me is what you’re doing in the meantime to fix sales in short order. Win or lose that’ll be incredibly valuable additional experience.
Do you have a performance review process? Run weekly/monthly 1 on 1 meetings with her and treat it as a coaching session. You already know areas where she needs to improve, so your goals are pretty easy to identify. The key to these is communicating and showing that you expect to see self reflection and growth in the role.
The reality is you either made a bad hire, or you’ve done a poor job training/mentoring/managing this person to date. That’s not meant in any mean context, it’s difficult to get right and it varies widely by employee. I’ve had great success with some and really struggled with others.