I have a 5 year old female Chihuahua (Lola) and we just recently introduced an 8 week old male shih Tzu, (Dobby), for the most part Lola tries to ignore him, but Dobby is very playful and everytime he sees her he wants to play either by laying down and
barking at her trying to get her attention or by getting close to her, Lola gets
annoyed and growls and she has bitten him twice (not hard, no blood involved) we do have some limits for him as he is not allowed in any room other
than the living room, during the day when we are at work, we put a crate up to create some separation.