From what's implied in the article, this lady said "cracker cops," while warning her daughter to be extra careful — and that's why she was forced to quit.
Are there actual white people somewhere who're actually offended by the term 'cracker'? None that I've known, but these snowflake cops were, and now they're no doubt chuckling about costing that African-American woman her job.
Just to add my thoughts: “cracker” could definitely be a racist term if used in this context. However, it will never have to meaning, connotation, or social stigma that the n-word does (especially spoken by a non-Black person).
The reason for this has nothing to do with one term being more racist than other (though that could easily be argued), but rather the social history. I’d be surprised if there are even a few lynchings of Whites, by Blacks, while that term was being yelled.
Historically, in America, Whites were the “top” racial group and Blacks were second class citizens at best. A disenfranchised group having a derogatory word for the group that is doing the disenfranchising will never have the same power as one used by a “ruling class” on this they are trying to oppress.