... but we are told specifically that Emma avoids contact with Miss Bates. There's at least as much reason to believe Emma avoided Miss Bates as there is to believe she was even minimally polite to her.

Ch. 19:
They were just approaching the house where lived Mrs. and Miss Bates. ... There was always sufficient reason for such an attention; Mrs. and Miss Bates loved to be called on, and she knew she was considered by the very few who presumed ever to see imperfection in her, as rather negligent in that respect, and as not contributing what she ought to the stock of their scanty comforts.
She had had many a hint from Mr. Knightley and some from her own heart, as to her deficiency—but none were equal to counteract the persuasion of its being very disagreeable,—a waste of time—tiresome women—and all the horror of being in danger of falling in with the second-rate and third-rate of Highbury, who were calling on them for ever, and therefore she seldom went near them.