Yes. With this and the moment where she doesn't resent Tom's selfish reason for dancing, it seems like she doesn't always care that much about selfishness. Not being involved is probably part of it, but I think the times she does care also involve people being inappropriate and/or hurtful. She thinks doing the play at all is inappropriate, so being selfish in the details doesn't stand out to her as being much worse. It's a little Dariaesque. Fanny starts caring again when she reads the play.

Poor Julia indeed. She gets to find out the hard way and doesn't have a really gracious way to back out now that she sees the situation more clearly. I know that feeling too, and it must be even worse because of the clear undercurrents of romance and rivalry.

I've just thought that it's like foreshadowing for her eventual fate. She rejects Mr. Yates in this instance, and accepts him when the Henry-Maria situation is even worse because her lack of good options is worse.