Well, working backwards, the "KNOTS in DALLAS" episode has Val staying in the same Dallas hotel as Gary and Abby while on a book signing, yet they keep narrowly missing each other and remain unaware of each other's presence until the final scene. For that narrative device to work, Val needs to be completely removed from whatever's going on at Southfork in the present (even if she does run into JR at one point). And so the viewer is left to fill in the blanks about why she doesn't even consider seeing Lucy: maybe the years they spent apart mean they can never be truly reconciled and/or Val is so devastated by the breakdown of her marriage that she cannot face any of Gary's family, including their daughter. I kind of like that it's left up in the air.