Embustera is the feminine form of embustero, which means "liar". It's a strong, emotional word used to accuse someone of being deceitful.
In the song, the singer sets a confrontational tone by saying, "Tú lo que eres es una embustera" (What you are is a liar). He uses this word to challenge a woman who is denying their shared past, making it a key to understanding the track's dramatic story.
This song is incredibly direct, and that's what makes it so fun! Beéle and Ozuna are talking to a girl who is pretending she doesn't know them or that nothing ever happened between them. They are not having it. The singer calls her out right away, saying, "Tú lo que eres es una embustera porque, mami, te culeé" [What you are is a liar because, mami, I f*cked you]. It's a very blunt and confident way to state his case.
He basically tells her that she can try to forget him, but it's too late. He sings, "Bórrame, elimíname, bloquéame / Pero ya te culeé, y desculeo no hay" [Erase me, delete me, block me / But I already fcked you, and there's no un-fcking]. The whole song has this playful but confrontational energy, all set to a beat that makes you want to dance, just like the chorus says: "Y la baila, y la goza, y la canta" [And she dances it, and she enjoys it, and she sings it].