My guess is that it went this way:
Eleanor Adeline UNKNOWN married a Mr HUDSON and they had:
Ella Etta, Ada Woods (who became GARDINER), and possibly even Robert Allen
Then Mr HUDSON died
Eleanor Adeline HUDSON remarried, this time to Robert George GILLAN
That's the main way I can think of that Ada Woods HUDSON became Ada Woods (Hudson) GARDINER
Just a thought?