I don't talk to people about what we spend on dog food, honestly it just doesn't ever come up and I know a lot of people who have dogs (basically everyone I know has dogs...). They don't ask, and I'm not looking for approval from anyone on anything pertaining to our pets so I wouldn't bring it up for any reason.
As far as your grocery budget, I think you still live at home so perhaps you don't think about what your mom spends on food a month? Because I just can't imagine at all how a person can sustain on only $100 in groceries a month unless you are emaciated and live on peanut butter sandwiches and raman noodles. Unless that isn't including lots of meals eating out and whatnot or you have a garden/farm that you grow a lot of your own food in (though to be fair you'd have to factor in all that goes into the garden/farm and deduct what you spent vs what you saved).