General:
* Model
* Theory
* Paradigm
* Structure
* System
* Perspective
* Approach
* Lens
* Conceptualization
* Schema
More specific to sociology:
* Theoretical framework
* Analytical framework
* Conceptual framework
* Methodological framework
* Social structure
* Social theory
* Sociological paradigm
The best word to use will depend on the specific context of Sima's studies. For example, if she is discussing the different ways that sociologists view the world, she might use the word "paradigm." If she is discussing a specific set of ideas that she uses to analyze data, she might use the word "theoretical framework."
It's also worth noting that "framework" is a very common and versatile word, so it's often perfectly acceptable to simply use it.