«Help, should my lesbian daughter take her girlfriend to the family party?»

It's wonderful that your daughter can live out her homosexuality with her parents' blessing. Register your daughter's girlfriend with her mother for the party, but don't submit to her discriminatory world view. That would send an ambivalent signal of acceptance to your daughter.

How nice that your daughter has an open-minded, supportive mother who is also prepared to accept conflicts with the family in order to send a signal: We stand by you, our daughter, and your relationship. You should also maintain this clear attitude towards your mother. If she is not yet aware of the partnership, it would be easier for everyone if she is informed in advance so that she can get used to the idea. If the relationship with your granddaughter is important to your mother, she will come to an arrangement.

When it comes to your mother's view of the world, the question arises as to who ultimately has to give way: the world or the image. I'm afraid the world is ultimately stronger. If your daughter really wants to go to the family party with her friend, then she will go just like all the other younger family members with their boyfriends or girlfriends. (Which is pretty sweet when 16-year-olds still want to go to family parties). If that upsets your mum, then that upsets her. And if she's being rude or indecent to your daughter, then you need to let her know briefly and clearly. Preferably in such a way that she is thoroughly ashamed.

