The correct translation of the word "hermanita" to the English is:
<u>Little sister</u>.
Explanation:
In Spanish, diminutives are constantly used that <u>serve to mention a person with a pleasant to somebody, either to make the person feel confident or to show friendship or familiarity with said person</u>, such diminutive ones usually end in <em>"ito; ita; itos; itas"</em> although in countries like Colombia they usually end up in <em>"ico; ica; icos; icas,"</em> but they will always be a way of saying <u><em>"little"</em></u> to the noun, whether it is true or not.