My absence would give that drinking session a common theme - "the disrespectful assholes who didn't show up for their Grandmother". You can't win with people like this.
You could try outNing them on this one. Break down in tears at the end and have to be helped away by your spouse. Have her return and whisper (loudly) to several people that you are so distraught at the whole event that you need to go home. You don't want to upset anyone with your grief. This way you escape, and they can't call you names.
That is what my mum does. Every single funeral she goes to. She
loves them.
Every single funeral she goes to is for her mother and father. She steals them. She steals any event she goes to, and puts it into her pocket as a trophy.
Then she lets herself get talked into going to the wake, and sobbing her way through that too, while everyone else is beginning to talk about the good times, and remember the deceased person with some dignity.
My mum once went to a wedding (of a cousin of mine) and spent the whole time collapsing into people's arms - our family and the other side!!! -and telling them that my (then) husband had taken an overdose the day before. It was true, but not the whole truth. There was never any danger. I looked on in embarassment, very angry that she even mentioned it. She stole that event too. She steals anything and everything she can get supply from.