Explaining to my child why I don’t speak with my mother

Hi everyone! I’m still many years away from having this conversation with my daughter (FTM with a 4mo), but I’m just so curious to hear from others.
I went no contact with my mother a little over a year ago (lifelong trauma, abandonment, has not changed and only gotten worse in recent years), but I imagine one day my daughter will ask about her biological grandmother. For those with similar experiences, what did you tell your kids when that time came?