Re: Pet Vs Boy

 First of all, you're not a "boy," even in jest - at this point in your life, you should be mature enough to recognize this gal's need for this wayward dog.  Man v Dog is more appropriate. 

This woman had her dog long before you came into the picture and, unless the topic never came up in conversation-before-getting-laid, you were aware of this dog.  If you truly feel that she is unable to control and/or manage the dog's behaviors and are willing to continue a relationship with her if her dog will OBEY, it may help to gently suggest obedience classes to her and speak plainly about your concerns.  If the dog's behaviors are annoying, dangerous, and out of control, this would not be unreasonable, at all.  A well-behaved dog is a companion for life, and you might grow to enjoy this dog if it were properly trained.

If this dog were going to cause issues within my personal relationship, I would gently bow out and go along my merry way, especially after having only dated this person for 3 months - Life's too short.  Declaring an ultimatum after only 3 months would be outrageous, petty, and selfish, I feel.   

Pets and animals provide unconditional love and acceptance.  They do not withhold their love because we are fat, ugly, stupid, blind, deaf, arrogant, cheap, wealthy, disabled, or any other human issue.  They love us without reservation - something that human beings should be striving to achieve.  

Best wishes.