They want to capture Isabel Aretas, a Mexican crime lord.
I haven't seen the movie but the plot description on Wikipedia is pretty detailed:
The main antagonist is
Isabel Aretas, widow of cartel kingpin Benito,
that enacts her revenge on the police officers responsible of her husband's death. Among them is Mike Lowry (Will Smith's character) and Captain Howard. This leads Mike, his partner Marcus Burnett (Martin Lawrence), and their teammates to go to Mexico:
Mike ultimately remained loyal to the police, realizing how dangerous Isabel had become. Despite Mike's opposition, Marcus and AMMO join him in Mexico City to confront her.
"her" in the sentence clearly refer to Isabel. This is very likely to be the same in the scene in the OP.
Also, there seem to be only two main female characters in the movie: the antagonist Isabel and Mike and Marcus' new teammate Rita. Since Rita is speaking in that scene, the only remaining possibility is Isabel.