Hormones! She's getting wiser.. don't mess with hens on the nest.. seems like a simple enough rule to me.
Add roll away nest boxes that can be collected from without disturbing a laying hen maybe.. it's critical to her life she get that egg out and maybe part pf the lesson for the kids.. patience is a virtue and when she's done she'll let you know.. also a mama will fiercely protect her offspring, even the unborn!
If it's truly an issue and the hen is the one who need correction instead of the hen being persuaded.. then I'd re-home. Otherwise.. doing in shielded makes the most amount of sense..
To me, she may have been confused at first and has now decided that nest raiding is completely unacceptable.. Disturb them enough times.. a nest hider may be encouraged to seek peace elsewhere.
Ah yes, it's nearly impossible to keep nests bedded.. You might go with a nest mat of sorts that is one solid piece and won't scratch out. I built deeper nests. Figuring out what works for YOUR flock might be a process.