Güerita is a diminutive of güera, which means 'blonde' in Mexican Spanish. It's a common term of endearment or description for a blonde woman.
In the song, the artist uses güerita to describe one of the two women he's involved with, highlighting her hair color as a distinguishing feature. It's a culturally specific term that adds a touch of colloquial charm to the lyrics.
In "GUERITA Y MORENA," Tito Double P tells the story of a man caught between two very different women. He calls them the "güerita" (the fair-skinned one) and the "morena" (the dark-skinned one). The singer describes himself as "weak" because he can't choose between them, even though he knows it might lead to trouble.
The song is a playful comparison of the two women's contrasting styles and personalities. For example: