No. There is no treatment for LL. And yes, if it's found in Lorraine's organs, your flock will then be assumed to carry this virus. No, it is not the end of the world. My flock has been living with LL for sixteen years. Most baby chicks I've introduced into my flock have been able to develop resistance to the virus and live normal, otherwise healthy life spans.
Things you cannot do are to hatch from within your flock as they will die in the egg or within a few months of hatch, introduce older chickens into the flock as they will have no resistance and have a good chance of developing tumors, and you may not rehome or sell hatching eggs or chickens from your flock.
While being similar to Marek's in many ways, LL is much easier to live with and has far lower mortality if you adjust to managing your flock with the few limitations I mentioned.