Qué poca is a colloquial Spanish expression that literally translates to "how little." However, in this song, it's used to express strong disapproval, disappointment, or even outrage, similar to saying "how lame," "how messed up," or "that's really low."
Ana Bárbara uses it to convey her disgust and anger towards her ex-partner's actions, highlighting his lack of respect and decency. It's a very common and expressive phrase in everyday Spanish that adds a lot of punch to the lyrics.
Ana Bárbara is not holding back in "Que Poca"! This song is a fiery anthem of a woman who's had enough of her cheating partner. She starts by calling him out, saying he thought he was slick trying to hide his affair, but she's "bien lista" [very smart] and caught him anyway.
Oh, and the other woman? She's "La Nacha," and apparently, she treats him "como a una cucaracha" [like a cockroach]! Ana Bárbara makes it clear that his misery is his own fault, telling him, "toda tu desgracia, tú mismo la decidiste" [all your misfortune, you yourself decided it]. She's not going to beg, and she's definitely not sticking around with a guy who doesn't even make her feel anything, especially after catching him "poniéndome el cuerno con otra" [cheating on me with another]. She hilariously declares, "Yo ni loca / Me quedo con un tipo que ni ganas me provoca" [Not even crazy / I'm staying with a guy who doesn't even turn me on]. She's not cleaning his house or washing his clothes, and she even found out his friend was the one who introduced him to the woman he was kissing! Talk about a double betrayal! This song is all about knowing your worth and kicking a cheater to the curb with zero regrets.