I wouldn't exactly say they "tossed her away", she just wasn't relevant to the plot. Would it have been nice to see where Picard ended up after the show? Sure. Was it necessary? Not really. I think there's something to be said about leaving a detail like that up to the fans to consider. You're going disappoint Team Bev or Team Laris one way or another, so you can just ship whoever you want in your head.
I'm on Team Bev myself. Laris feels much more like a right place, right time fling. She was kind of vulnerable herself having just lost Zhaban. The actual romance was super short, and now Picard finds out he has a kid and reconnects with the real love interest that he messed up 20 years ago... I feel like there's much more there. It's a nice circular story too... Picard loses Crusher, finds Laris, Laris loses Zhaban, finds Picard, Picard finds Crusher, Laris loses Picard. Ultimately sad for Laris, but at the same point she did have the opportunity to have a long, fruitful marriage... Picard and Crusher did not. They deserve it.