Ehhhh... Who 2 plushes suggest that she can betray him??though it also seems likely that Flatline could try to get close to him just to betray him. After all, she's a villain's sidekick - not a hero's. This aspect is further pushed by the pair of plushes in the background of Robin and Flatline, sitting atop previous volumes of the manga series.
https://screenrant.com/robin-flatlin...ver-dc-comics/