My Mom Won't let me get another Dog ?

I Really Want another Dog , my mom always says yes then she backs out of it for no reason apparently ? Our other dog is really hers and has a Bad attitude towards me . It's not really even a Dog , i have asked for other pets ( Rabbits , Ferrets ) and she still says no , i save up my money cut the grass for free , do stuff without being told Keep My room clean living room clean . Walk Her dog , then she says i spend too much time on facebook ( untruthful ) , only get on later in the day except weekends . Then i say well if i had something else to do , i wouldn't spend so much time on there , i dont really have alot of friend and really dont go out with my few friends once or twice a year . I want a Chocolate Lab or a Golden Retriver or possibly a Cocker Spaniel , her favorite breeds but she says No ! I'm not a Bad Pet owner . with my past pets ( Birds ) , BTW thats the only thing she WILL let me have . And i dont want another !