Hello there Hoai-An,
Welcome to planDisney and thank you so much for the question! I love the fact that it's so easy to link tickets in the
Disneyland mobile app - it makes visiting the parks with a group so much easier!
I'm happy to share that you can also make changes to your
Disney Genie+ Lightning Lane selections within the mobile app. You'll just need to link your ticket to your app, so your sister will need to send you the ticket ID number for you to complete that step.
Since you've already purchased your tickets, you'll need to wait until you scan into the parks for the first time during your visit to purchase the
Disney Genie+ service (as you can currently only purchase it when you purchase your tickets or when you arrive in the parks for your visit). Once that happens, you and your sister will be able to make Lightning Lane selections for one or both of you as you are eligible for them.
I visited the Disneyland Resort with a group of friends last December and we linked our tickets together so that one of our friends could make Lightning Lane selections for our whole group at once. It was so convenient! Then, when a few of us broke away from the larger group, we were still able to make our own individual selections as we were eligible to make them.
I hope that helps! Thanks again for your question, Hoai-An, and have a fantastic visit to the Happiest Place on Earth!
Have a Magical Day,
Greg