Answer
24 years.
Work Step by Step
The value of $\gamma$ is $\frac{1}{\sqrt{1-u^{2}/c^{2}}}=8.466$.
To the astronaut, the trip appears to take a time of $\frac{42.2 ly}{(0.9930c) \gamma}=4.98 years$.
She started at age 19, so ends up being age 24.
