What is the meaning of - le voy a decir mi hermana cuando llega papa?

The sentence "le voy a decir mi hermana cuando llega papa" is grammatically incorrect in Spanish. There are several possible interpretations depending on what the speaker intended to say:

1. "I'm going to tell my sister when dad arrives":

* Correct: "Le voy a decir a mi hermana cuando llegue papá."

2. "I'm going to tell her sister when dad arrives":

* Correct: "Le voy a decir a su hermana cuando llegue papá."

3. "I'm going to tell her when dad arrives to my sister":

* Correct: "Le voy a decir a ella cuando llegue papá a mi hermana."

Explanation of the errors:

* "le": This pronoun needs an object (the person being told). It should be followed by "a" + the person.

* "mi hermana": This phrase needs a preposition ("a" or "de") before it depending on the intended meaning.

* "papa": This should be capitalized as it is a proper noun referring to the father.

Therefore, you need to clarify what the speaker meant to say to provide a correct and accurate translation.