My grandma makes me want to cry

Tell me if I'm over reacting. Me and my mom are really close. We are basically best friends. I moved 2 and a half hours away from her so we barely get to see each other now. And her work schedule is crazy so we barely get to talk. But every time I make plans to go visit my mom my grandma (step dads mom) always happens to go that day. So this weekend I wanted to go visit but my mom said my grandma was coming up on Saturday to go to a festival so we wouldn't be able to do it this weekend. I texted my step dad and made plans to surprise my mom tomorrow. They had no plans tomorrow so everything was set to go. I was going to park my car behind the garage so she wouldn't see it when she pulled in when she got home from work. I made a post on Facebook about surprising my mom. And just so happens my grandma said she is going up tomorrow too when she wasn't supposed to. I don't know if it's my hormones but I'm shaking I'm so mad. I just want alone time with my mom and I can't even do that because she always has to be there. Mind you she only lives 20 minutes away from her where as I live 2 and a half hours away. Am I wrong for being upset?