What the Bible says about Martha's Service
(From Forerunner Commentary)
Though Martha's service was undoubtedly good, in this case her judgment told her to serve in an inappropriate way, and Jesus corrected her. She thought she was being kind to Him, but resentment was building in her, and her kindness was misplaced. In reality, all her activity was insensitive to the situation and resulted in her being mildly chastised. Martha loved Jesus and intended to be kind, but she gave her "kindness" in her own way, more or less forcing it upon the situation whether anybody else liked it or not. She produced an unintentional unkindness to the situation and to Jesus.
John W. Ritenbaugh
The Beatitudes, Part 5: Blessed Are the Merciful