paragraph: Olivia had long suspected Ellis of feeling a more than friendly interest in Clara. Herself partial to Tom, she had more than once thought it hardly fair to Delamere, or even to Clara, who was young and impressionable, to have another young man constantly about the house. True, there had seemed to be no great danger, for Ellis had neither the family nor the means to make him a suitable match for the major's sister; nor had Clara made any secret of her dislike for Ellis, or of her resentment for his supposed depreciation of Delamere. Mrs. Carteret was inclined to a more just and reasonable view of Ellis's conduct in this matter, but nevertheless did not deem it wise to undeceive Clara. Dislike was a stout barrier, which remorse might have broken down. The major, absorbed in schemes of empire and dreams of his child's future, had not become cognizant of the affair. His wife, out of friendship for Tom, had refrained from mentioning it; while the major, with a delicate regard for Clara's feelings, had said nothing at home in regard to his interview with her lover. 
question: Why did Olivia not want Ellis around the house?
answer: He was inappropriately interested in Clara, and she felt it was not good to have him around a young lady all the time