“She probably returned because she was told to.”
If that’s the case, whoever told her to return (on a plane and exposing over one hundred people) should be severely reprimanded. The nurse should have been told to report to quarantine in place until further notice.
They should have sent someone to ‘fetch’ her. Nigeria did with their nurse escapee. Putting her in quarantine somewhere else increases the number of potential exposures from another hospital cluster.