Anna walks $15\text{ meters}$ south, then turns right and walks another $20\text{ meters}$. How far and in which direction is she from her starting point?

Let the starting point be $O(0,0)$.
1. Anna walks $15\text{ meters}$ south to reach point $A(0,-15)$.
2. Turning right while facing south means she will head west. She walks $20\text{ meters}$ to reach point $B(-20,-15)$.

The shortest distance from the starting point $O$ to final point $B$ forms a right-angled triangle $OAB$:

$$\text{Distance }OB=\sqrt{O{A}^2+A{B}^2}=\sqrt{15^2+20^2}=\sqrt{225+400}=\sqrt{625}=25\text{ meters}$$

With respect to the starting point, the position $(-20,-15)$ lies in the South-West direction.
Therefore, she is $25\text{ meters}$ south-west from her starting point.