OP here. Thanks for all the support and funny comments. To clear a few things up, my sister didn't post to Instagram from the hospital, she just took a selfie at home and complained about the things that aren't going well in her life. She had no idea that I didn't know about my grandpa and assumed that our mom had told me. Since my sister and I both live at home, our family tells my mom about any big family news with the assumption that she will pass it on. Right now, my mom is in a really busy period at work and I'm an American exchange student in New Zealand, so I'm sure she wasn't purposely hiding anything from me. Since I go away for college, she sometimes forgets to tell me things anyway.