La versus Lo

Question

HelloI do not understand why you use « la » in this sentence?Se la estamos decorando.We are decorating it for him.

Accepted Answer

Hola Sylvie
In these two sentences from the lesson, (meaning the same):

Estamos decorándosela.
We are decorating it for him.
Se la estamos decorando.
We are decorating it for him.

"la" is referring to something, a noun,  that is feminine singular, say for example the referent is "la habitación" (the bedroom):

Estamos decorando la habitación de Lucas.
Se la estamos decorando.
Estamos decoránsosela.

If the referent were a masculine singular noun, for example, "el dormitorio" which is also another word for "bedroom" but masculine, we would use the masculine pronoun "lo" instead:

Estamos decorando el dormitorio de Lucas.
Se lo estamos decorando.
Estamos decorándoselo.

I hope this clarifies it for you.
Un saludo
Inma