Devise a plan with your best friend(gf and her best friend) to lie about getting together with her boyfriend after 10pm on New Years eve(after going out with her friends for dinner and then hooking up with boyfriend) and in reality hooking up with her real date and guy she had been seeing for about month leading to this on the down low. Contiunually put off seeing boyfriend the day of new years eve, acting very suspicious, so much so that boyfriend knew something was up and went to her place, got all of his stuff while she was out and grabbed his dog and left the key to her place on her night table by bed(which turned out to be a very good thing, because the plan was to try and keep his dog just to get in another dig on him for no reason, which would have been a very bad outcome, because nothing comes in between the boyfriend and his dog). When 10pm rolls around, make up stupid lie about staying out till 11:30pm, then stop answering the cell phone and then have her friend, send a text at 12:30am NYE from her phone, saying it's over, have a good life and send a pic of her in stupid embrace with some idiot).

Then the next day try to come over and ask why ask why the key was left and why the dog was gone. Sucked for about a day, but when hugging his dog, the now exbf realized just how good things really turn out and how now life was going to be good again.