This is not an uncommon reaction to anti-depressants for a woman of childbearing age. You are correct, monthly fluctuations in hormonal levels can account for a great variance in mood stabilization. And, it is not (unfortunately) an infrequent process to see medications change at 6-9 month intervals.
Why is this so? There is only so long a neural cell can be encouraged chemically to absorb more serotonin. In most people, 1-2 years is a common therapeutic interval, but in some people, especially women, this interval is much shorter. As a result, various medication combinations are used with greater frequency.
Adderal in adults has been used in the fashion you describe, although not all psychiatrists will use this combination for treating depression. Yes, the Adderal can act paradoxically, causing relaxation and sleep.
As your wife may have metabolic issues, a best practice is to see an endocrinologist, who can evaluate her hormonal, renal, hepatic and metabolic processes to see if her biochemistry is indeed a culprit in her response to medication. I will also say that some research on effective stabilization of mood also encourages the use of natural supplements in combination with medication.
Your wife many wish to gain permission to take 1000mg of Omega Three Fatty Acid per day along with 100 mg of Magnesium glycinate, 100 mg of Calcium and 10 mg of Zinc. Research in the US and UK shows promising stabilization of mood with this combination. Steven