I really had no intention of using Jaheira much in my party despite fond memories of BG1 & BG2. TBH, my feeling was that the tie-ins to the earlier games were among the least interesting aspects of this game, and on the whole I'd prefer a completely new story.
However, Jaheira in Baldur's Gate 3 is an excellent character; she's a lot more interesting here than in either of the old games. And as a companion, she adds a LOT to the experience of Act 3. And the nostalgia elements ended up being done just right imo. She's become a mainstay in the party for Act 3 for me.