You must establish yourself as a strong pack leader or she will think that she is. Try some submission training, and make her work for meals, treats etc. Mastiffs in particular love to please, so giving them commands that they must then follow before rewarding serves two purposes. It gives them a "job" and it reminds them of your role as pack leader. Hope this helps... good luck.
Answered by Anonymous - 11/11/2012 1:44:21 PM