I'm going to show my mom that I have stuff planned
Why are you going to show your mom that you got stuff planned?
I heard she wants to do stuff alone with me and it will probably take a lot time
You shouldn't lie to avoid spending time with your mother. She probably misses you a lot and just wants to spend quality time with you. One day when your mom passes away you will wish you can spend time with her.
Fuck my mom, she should be dying and not bothering me.
Lying to avoid spending time with your mother is wrong. If you have a good reason for not wanting to spend time with her than that is understandable, however with the information I have right now it sounds like you are the one in the wrong here. Hopefully you understand where I am coming from with what I am saying here.