Mastiff aggression towards small animals

Question
Hi, I am hoping you can help me out here and will truly appreciate an honest answer even if it is not what I am hoping to hear.  We have an English Mastiff that is nearly two years old.  She is our housepet and seems to do very well with our four small children..very tolerant with them.  She seems to have an ongoing issue with attacking small animals, at first it was kittens, and then several incidents with smaller dogs.  The first being we had brought home a new mastiff (male) puppy and my husband was standing holding him and we wanted to introduce them outside, she jumped up and tried to take him from my husband causing him to drop the puppy and he literally had to wrestle her to the ground to get her to stop trying to get this puppy.  We kept them separated until he grew larger and she is totally fine with him now.  Secondly, a neighbor lady came over and was outside with her smaller dog on a leash, one of the children must have let Chloe outside and she dove for this dog and the lady and I both had to fight to get her away from this dog..the lady was pretty much swinging her dog by the leash and dangling it to keep it from Chloe.  The most recent and by far the worst was my sis coming over for Thanksgiving, her boyfriend walked in the back door with there Chihuahua mix in his arms, (we would have put Chloe up had we realized they were bringing their dog).  Chloe jumped up and took the dog right out of his arms as soon as they got in the door and in spite of my sister hitting her and telling her to stop, she proceeded to kill the puppy.  The strange thing is, she shows no human aggression whatsoever, people come over and she just loves them to death, she also seems fine with larger animals (we have a neo mastiff as well as 2 other English, she is fine with them, can eat with them and everything, even lays on the ground if the male growls at her ) and has not killed our cat.  Just kittens and small dogs.  The part that is the scariest to me is that when she does this, it is pretty near impossible to stop her, you can literally yell at her try to pull her off,  and even hit  her and it is as if you do not even exist.  Also, as far as we can remember, she does not snarl, growl, or have raised hackles when she is doing this, it is just a quick attack as if she has gone crazy.  She gets the animal in her mouth and shakes it and in the case of my sisters dog as well as kittens, punctures and kills them.  It is horrible and I consulted the vet about this and was told it is not normal for the mastiff breed and also there would be a concern for if she became aggressive with the children.  She seems to love people and be very tolerant, but I am of course worried and as I said, my biggest concern is the fact that when she is doing this, there is pretty much no stopping her without great physical force (such as my 230 pound husband literally wrestling her to the ground and holding her ), in the case of the kitten, I even grabbed a board and broke it trying to spank her and stop her.  It is really scary and I am considering finding her a new home as I am afraid of her getting out of the house and going after someone's dog they are walking by.  My husband is not wanting that at all, and I would prefer to keep her myself, but also want to do the responsible thing.  She has had a litter of puppies at the end of July and she is not in heat currently.  Sorry this is so lengthy, hope you can help us out here.  Thanks so much!!!!   ~~Jennifer

Answer
She has a very high prey drive and no respect for anyone in your home as alpha. The best answers are usually not easy ones. Get her into an obedience program immediately. She can EASILY go from small animals to small children. the prey response is the same. Also go to Alpha Boot Camp (type it in in your browsers search window) and read the site until you really KNOW it and can implement it. Rehoming her will only pass the problem off to someone else. Spanking her is useless and is likely to result in getting bitten. Hitting is not something a dog understands. WALK her as much as possible if you can do so safely if not wait until you get her into obedience and meanwhile exercise her as MUCH as possible every day. Tired dogs are good dogs.
Diane