Here's another possible scenario for resolution, probably temporary, of the canonical problems with this convent. There is such an arrangement as a "Metochion," essentially a satellite (I can't think of the ecclesial term in English), wherein, the monastery could remain under the bishop in Greece. The Greek Orthodox Archdiocese of America has been opposed to such an arrangement in the past; it took probably more that a decade to rein in Fr. Ephraim's monasteries, but several years ago, all of them accepted the GOAA's Uniform Monastery Regulations.
Here's another wild option. The GOAA or the Antiochian Orthodox Christian Archdiocese of North America take them in and force compliance with their respective uniform regulations; probably the abbess wouldn't accept them, though, because the Archdiocese would have authority over the property, the nuns, and the election of the abbess. But if the abbess refuses to comply with provisions of the uniform regulations, the abbess could be dismissed and then the monastery could be operated canonically. This probably isn't realistic because the abbess wouldn't accept the terms of the archdiocesan regulations to begin with. But if their current spiritual father in Greece could talk the abbess into accepting hierarchical authority from ecclesial authorities in their nation of residence, the U.S., the monastery could be saved for canonical Orthodoxy. Who knows, ROCOR may have already tried this approach.
From what I'm reading, except for the episcopal oversight issue, a major issue no doubt, there is a good deal of holiness in this monastic community and the church should be able to creatively negotiate a canonical arrangement with these nuns; perhaps there is a rational cleric in Greece who could convince the abbess of the absolute need to accept canonical oversight. Perhaps OCA Bishop Melchizedek of Pittsburgh could advise the GOAA or the AOCANA of some sources in Greece who could be accessed for this purpose.