she does not USE her as a companion for her fahter. She is glad that Miss Bates is there to be a pleasant companion for him, and He likes her and enjoys her conversation. Its not as if Emma has Miss Bates carted up to hte house every night, while she herself goes out dancing..
yes she does not find Miss B all that amusing herself, who would if htey had to live wiht her? unless they were like Mr Woodhouse rather silly as well? She DOES fall down on her duty to clall more often on Miss B, but she's not perfect...