Her conditional GC is expired. Lacking a pending I-751, as far as DHS is concerned her LPR status will have expired. I am certain she would be admitted into the country, but I fear she would get an NTA, or worse, and NTA and be turned over to ICE for detention pending her removal trial trial.
Having filed 6 months late, even if she gets her 48 month extension letter, I think it is too risky for her to travel outside the U.S.