My family has an 8 year old female Boston terrier mix that we adopted from the SPCA back in June. Recently she has been deficating and urinating all over the house. Tonight, when our house mate was attempting to clean up the mess, Margie (our dog) bit her. She has also bit my wife once before during a similar situation. Now this only happens when I am not home. I'm looking for any advice and guideance here as I don't not want to lose Margie.