As I expected the trailer didn't tell me anything useful or meaningful. It's a movie trailer, which makes sense as BG3 is more a movie than a video game. Just lots of pointless cinematic fluff.
If Jaheira is going to be a party companion, then she will be the first, and thus far only companion choice I would truly like having in my party. And it speaks volumes that Larian has to go dredge up old companion characters from the first game made 22 years ago to come up with memorable and enjoyable companion characters. Even in BG3, the credit for Jaheira (and Minsc) go to Bioware and not to Larian.