I am sorry to know of your daughter-in-law's demise at such a young age. Heavy smoking
is definitely known to increase the risk of heart attack
and would definitely have contributed to it. Regarding the pain and anxiety
medications she was abusing, it would depend on what she was taking, since when and in what dosage. In the absence of this information, I can only say that it is possible that the medications might also have contributed to the heart attack. Diet is a very important factor in improving cardiac status, and therefore it is likely to have had a bearing on the heart attack.
Please accept my condolences. Wishing you all the best.