bath you obviously lack basic empathy. I genuinely think you might want to look into that.
I lack empathy for a man trying to take off for three days for a funeral he had no good reason to attend.
You lack empathy for the woman being expected to cover his self-indulgence at no notice and without consultation.
Maybe you should look into that?
The idea that if someone wants to attend any funeral of anyone they've ever met, no matter how far away, or how inconvenient for other people, that it is automatically and definitely the right thing to do is so stupid I shouldn't be surprised to see so much of it trotted out here.
There are lots of ways to mourn and pay respects.
The standard thing to do for a sister's close friend (where you don't know the family), when the wedding is far away, is to send a condolence letter to the family, expressing your sadness at the parting, and with some nice stories about the deceased. You can also send flowers and/or donate to a nominated charity.
Then you support your grieving sister at home. In all the small ways people need.
Making a grand statement 3 day excursion to the funeral of someone you were not close to, when you don't know the family well, is just bizarre.
I can't see where there is any empathy at all for the family who have just lost a loved one in this plan, or the support of it at all costs.