@a mamin
Slang is a word such as ain’t. A nickname is NOT slang, it is an endearment. In this case as the OP wrote it is the English verbiage which would have the endearing name, not the proper Hebrew inscription.
My father’s stone have the correct Hebrew name, in English it has his given name then a parentheses containing A/K/A XXX…….the name everyone knew him as for more than 90 years.
In the OP’s case the great grandchildren will go and visit the grave for many decades to come and be comforted to see that ‘Bubs’ is buried there. They do not know her by any other name.