i recently adopted a 4 year old female min pin from the shelter and it seems like her prev owner allowed her to eat human food all the time. when we eat any meal or have food in car with her she goes insanely ridiculosy crazy trying to get to it and will do whatever it takes to get to the food. she also seems like they allowed her to have no rules. if you attempt to take food away from her that she got into she snaps and growls. what do i do to break this habit?