"Mother's Little Helper" relies on a bit of metaphoric magic. The "helper" here does not refer to a cooperative little sprite running around mom's kitchen but rather a "little yellow pill," as in: "Mother needs something today to calm her down/And though she's not really ill, there's a little yellow pill. . . ."
Things don't end happily for this mother, as the song ends: "No more running to the shelter of a mother's little helper/They just helped you on your way through your busy dying day."