In English it's more natural to say she changes (her) identity, singular.
Maybe she is an administrator in a witness protection program.
hee machalifa zehuyot
הִיא מַחֲלִיפָה זֶהוּיוֹת
להחליף also means exchange, right?
Correct. To exchange
Could she be logging into her second Duolingo account?
"Identity" as in she changes her character, gender or she pretends/acts as someone else?
Well, it means the latter, to pretend to be someone else. זֶהוּת is a curious modern word formation, using זֶה "this" and the suffix for abstract concepts ־וּת
Oh, cool, so זהות is like "this-ness."
Or - could it be that she is a system administrator changing the identities of the SW users? Guessing that from the fact that it is not "הזהויות שלה".