The movie is subtitled when Elisa has no translator & we need to know what she's saying...
At the point, we see her sign 'trivial' & Zelda translates for Strickland [& the audience]
After they are dismissed, she quickly signs something for which there is neither inworld nor subtitle translation - after he asks her to "Say that again" she signs it slowly & the subs give us one letter at a time..
F ... U ... *... *... ..Y..O..U..
After Strickland asks a second time & Zelda translates as "Thank you" then we are back to accurate translation.
