Mr. Stelling’s wife is a woman to whom Tom takes an instant dislike. This is nothing new – Tom is notoriously judgmental and hard to please. Mrs. Stelling does contribute to Tom’s rather negative opinion of her though:
I am afraid he hated Mrs. Stelling, and contracted a lasting dislike to pale blonde ringlets and broad plaits as directly associated with haughtiness of manner and a frequent reference to other people’s "duty." (2.1.14)
She is a rather stuck-up woman and she is not very friendly towards Tom and Philip. In fact, she seems downright uncomfortable around them much of the time.