This whole situation really irks me. It would be one thing if you didn't like her, but you indicate that you have openly tried to include her and welcome her to the family. I don't know what her problem is to treat you this way. I don't know who she is, but I don't like her!
If she is going to throw etiquette out the window by not letting your family plan the rehearsal dinner or invite you to the dinner, then you should throw etiquette out the window and show up uninvited. But I know you're not going to do that. This is your brother, and it's the last night you'll have to spend w/ him before he's a married man, so if it were me, I'd be fighting tooth and nail to be there. But that's the last thing I'll say about that.
When I got married, my husband's mother told me what we were doing for the rehearsal dinner, then asked if it was okay, and who else did we need to invite. All I had to do was send the invitations and give her a final count. It worked well.
I still think she's acting this way b/c she's jealous of your relationship w/ your brother. She sounds too immature to be getting married!
This is why weddings are such a PITA. I firmly believe in eloping!
As far as wedding etiquette, here's a story: we just received an invitation for a friend of my husband's upcoming wedding. I was so mad b/c 1-the response envelope didn't have a stamp on it, and 2-it's a 6 o'clock wedding, and there's going to be a "dessert reception" following. Hello! If you're not serving dinner, then you need to have the wedding earlier or later. With a 6 pm wedding, that means the guests will most likely have to eat dinner at 4 pm! The couple lives in WA state. Maybe that's just how they do things out there.
ETA: You
are invited to the wedding, aren't you?
ETFA: Oh, almost forgot. This happened to my friend. Her fiancee's sister obviously didn't like the bride-to-be. At the rehearsal dinner, she (the groom's sister) gave him this scrapbook that she had made him w/ pages upon pages of pictures of him, his family and ex-girlfriends, and not a single picture of my friend. Of course, she was VERY upset. But this sounds like a nice gift you could give to your brother! Lol. Just kidding, of course.