I'm afraid there is no direct flight from Guilin to Lijiang, even no direct train and long-distance bus. Whatever transport you take, Kunming can be chosen as a transference place. Therefore, from Guilin, you can take a train to Kunming first, then transfer to train there to Lijiang. It is the same way if you wanna take the long-distance bus: Guilin - Kunming - Lijiang.