Surge accepts to be Gabrielle way later in the story, like after she turns into the L.Gaia Guardian, so she gives the freedom of choice to people to call her whatever they like more. Sonic, Jamala and other people in the Village call her "Gabry" (Sonic) "Gab" (Jamala), "Sister Gabrielle". People like Kit, Amy and other official character will keep calling her "Surge", even some baby tenrec in the village would call her "sister Surge" instead of "Gabrielle".