When BFF is invited to her niece's ballet recitals 1.5 hours away, she is adamant that she should not have to pay to see the show. I understand this: she has to travel and then suffer through the other children's "talent." And she has to be around her unpleasant brother. It's not about the money per se - she's not rich, but she can afford to pay. It's the principle. They're inviting her, it's a schlep, they should cover some costs.
Rereading your paragraph above, it sounds like you are trying to somehow figure out a justification for her expectation when it comes to her family events. But the thing is, those conditions don't apply when it comes to your daughter's show. So it's totally not
It's just some arbitrary rule that she has come up with for whatever justification she has in her own mind. But it is most certainly not the norm by any stretch of the imagination.
It seems to me that what she is doing is saying, "I'll come to the show, but only as a favor to you, and as such, you'll need to cover my costs." So... is her attendance a favor to you? Because from your description, it's apparently a reciprocal friendship, you do things for her, she does things for you, and it all evens out. She appears to be saying that attending your daughter's show is over and above
what she might consider the ordinary give and take of the friendship.
Now, that's perfectly fine for her to feel that way. I know that sitting through those shows when my own kids were in them was ok, but I wouldn't have exactly been thrilled to sit through them for friends' kids, whereas, going to friends' kids birthday parties, for example, would be normal and expected. In other words, sitting through recitals and plays of other people's kids really can be seen as "over and above".
I think it's totally presumptuous of her to expect
you to pay, and to come right out and ask for you to pay. But I can also see her thinking that she is sort of making a sacrifice by sitting through it as a gesture of friendship. Although why she feels like she needs to go to both nights is beyond me!
I think I might have a chat with her about this before the precedent gets set for life. Friend, I will be happy to pay for you for Friday night only, for this event only. Please don't feel obligated in any way to come to the Saturday night show. And please understand that we really can't pay for you to attend all future events so whenever it's a paid event, we'll completely understand if you decline to attend.