Vashti is a planet where Romulan refugees were resettled after the Romulan supernova and where the Qowat Milat raised Elnor.
Vashti is a world that took in Romulan evacuees before the attack on Mars halted Starfleet's rescue effort. Picard had helped relocate refugees there, and it was there that he befriended the young Elnor. After the evacuation collapsed, many of Vashti's Romulans came to resent the Federation for abandoning them, and the warrior nuns of the Qowat Milat kept a house on the planet.
In Absolute Candor, Picard detours La Sirena to Vashti to recruit the now grown Elnor. Picard is confronted by Romulans who blame him and Starfleet for their fate, and Elnor defends him with his blade before joining the crew.