In the summer of 1267, Stella was tasked by Emhyr to educate and take care of the girl thought to be Ciri, heiress to the throne of Cintra. However, when Stella formally presented the young girl to the emperor, she immediately recognized the feigned smile on Emhyr as one that would send heads rolling, though thankfully this wasn't directed at her. Following this, Stella and false Ciri were sent to Darn Rowan until "the arrival of more peaceful, happier times", though this was actually to buy time until they could locate the real Ciri.
At one point prior to being put in charge of Ciri, Stella became indebted to Fringilla Vigo and thus, when the sorceress asked for a lock of the girl's hair, Stella had no problems with sending her a small clipping, which Fringilla then used to prove to herself that it was indeed a false Ciri.
Early the following year, while still in Darn Rowan, the emperor visited to talk with her and false Ciri as the latter's portrait was being painted. Emhyr praised Stella on her work educating the apparent princess, even when she knew the truth about the girl. The Emperor then confessed to Stella that it was possible that the time to get rid of the girl was near, for reasons of state. A short time later, Stella arrived in the city of Nilfgaard with false Ciri and Emhyr decided to marry the young girl to secure Cintra as part of the Empire, forfeiting his original plan in order to not have to marry his daughter or kill the false one.
Stella ended up outliving both Emhyr and false Ciri and died in 1331, leaving her estate to distant relatives.
Effenberg and Talbot,
Encyclopaedia Maxima Mundi, vol. III