It can happen..Adderall is 'speed'. If she's been on that long, she's built up a tolerance and I bet, she's on a higher dosage.
I too, at 50 became so depressed and extremely sad for months. I was given Adderall and I was amazed at how quickly, within hours, my mood was elevated!! LOL. I remember telling myself, " I think this med. is making me happy"! I was concerned about the potential of addition...my Dr told me to use as needed. Presently, I am on no antidepressants:)