Gata literally translates to "female cat". However, in many Latin American countries, it's a common slang term for a woman, similar to "chick" or "girl" in English.
While it can sometimes be used in a derogatory way, in this song's context—"Mi Gata" (My Girl)—Junior H uses it as a term of endearment for the woman he misses. The entire song is a lament about losing his "gata," making this a central and memorable piece of slang to learn.
Junior H gives us a classic corrido tumbado heartbreak song with "MI GATA." The story is simple: his relationship is over, and he is absolutely miserable about it. He starts by saying she's no longer his, using the line "Ya no es mi Dom Péri y tampoco es mi gata" (She's no longer my Dom Pérignon and she's not my girl). He's trying to sound tough, but immediately admits her Chanel perfume still drives him crazy. The whole song is full of these sensory details, like how her scent lingers in his bedsheets and how the desire for her "me consumen" (consumes me).
He's not pretending to be over it. The chorus is a blunt confession: "Te voy a extrañar, ¿para qué te digo que no?" (I'm going to miss you, why would I say I'm not?). He knows he messed up, maybe because of his "mala fama" (bad reputation), and now he's left drinking whiskey and thinking about her. He even claims her friends know she still loves him and cries for him when she's drunk. It's a sad, self-aware song about missing someone so much it feels like you could die without them.