Questions & Answers about Mi hermana se pasa el día leyendo novelas en español.
It is a very common Spanish pattern: pasarse el día + gerund.
So Mi hermana se pasa el día leyendo novelas en español means My sister spends the whole day reading novels in Spanish or My sister spends all day reading novels in Spanish.
You should learn se pasa el día leyendo as a chunk, not word by word.
Here, se is part of the verb pasarse, which is often used in this expression.
It is not really reflexive in the English sense of herself. Spanish just uses the pronominal form in this idiomatic structure:
- pasarse el día estudiando
- pasarse la tarde hablando
- pasarse la noche trabajando
This structure often sounds very natural and colloquial in Spanish.