Made a promise to my toddler I cannot keep. How do I break the news to her that she's not going to get to see the new Star Wars?

So before Star Wars Last Jedi came out, we promised my 3.5 yr old that if she behaved well and got all her "good-girl" stickers on her chart, she could go to the movies (her first time ever) with us to see the new star wars. She's loved the force awakens, we watch it weekly.Upon seeing it first with my husband, we realised we messed up. It's a lot more gritty than the fun loving force awakens, and just not appropriate for someone her age. So what's going to be the best way to break it to her? She's going to be devastated.I have no clue what to do here, any help would be greatly appreciated!! via /r/Parenting http://ift.tt/2lJrcVg