though it is a good antidepressant, some patients express sense of fatigue and tiredness with the prescribed medication. You have an option to go back to your psychiatrist and get an alternative medication prescribed. Else you can also get a second opinion regarding the same. Meanwhile also get her general medical condition. Evaluated to see if any medical condition is contributing to underlying fatigue depression. Good luck.
Next Steps
Physician evaluation and second opinion if the psychiatrist is not able to address the issues.