Preeti starts from point $A$ and drives $7\text{km}$ towards South. From here, she takes a left turn and drives $9\text{km}$. She then takes a final left turn and drives $7\text{km}$ to reach point $B$. How far should Preeti drive to reach point $A$ from point $B$?

Let's plot Preeti's movements step-by-step using coordinate paths starting from point $A(0,0)$:
1. **From point $A$, drives $7\text{km}$ South:** Reaches position $(0,-7)$.
2. Takes a left turn (facing South, left turn means heading East): Drives $9\text{km}$ to reach position $(9,-7)$.
3. Takes a final left turn (facing East, left turn means heading North): Drives $7\text{km}$ to reach point $B$. The new position is $(9,-7+7)=(9,0)$.

Point $A$ is at $(0,0)$ and point $B$ is at $(9,0)$. The shortest straight-line distance between them is:

$$d=9-0=9\text{km}$$

Therefore, she needs to drive $9\text{km}$ to get back to point $A$.