It's interesting the first SO comment jumped onto covid extremism right away, when that had nothing to do with the question, and got a lot of points. That's not a good sign for SO, if it's going to bring politics into the questions and reward people who do.
Personally I think if there's not a performance issue, trying to enforce a policy "just because" is untenable. In this case, it seems like there was a performance issue, so that should be addressed.
Why even ask about this? The person's manager has to set, and enforce a deadline, or the employee has effectively negotiated a permanent work-from-home agreement. If you want to fire them, do so, but otherwise- the company failed at negotiation. The only thing the employee shouldn't do (if they are) is lie about the reason to stay home.
I expect this is a self-resolving problem. The employee in question is probably using a portion of that "not in the office" time to interview with companies that have more reasonable policies. If the OP just rides this out, it will probably become a non-issue soon.
I also narrowed in on key words like “she” and “daughter,” and realized the OP is a man who probably doesn’t have kids. This is the stuff that drives our women engineers out of the workforce.
Personally I think if there's not a performance issue, trying to enforce a policy "just because" is untenable. In this case, it seems like there was a performance issue, so that should be addressed.