I drank at my company party while my girlfriend was at home concerned about her grandpa being rushed to the hospital
Did you really leave your girlfriend and her grandfather in the hospital?
No, I only came home to say hello and say that I was tired. Then I went to a friend's house.
It's not respectful to consider your girlfriend's feelings while her family member is ill. Maybe you can check in with her to ask what support she needs? This will help show her that you support her.
I don't want to be a disappointment with her grandpa, so I'm going to tell her this whole story.
You will feel more of a disappointment if you don't show up when your girlfriend need you the most. If I were you you should try and visit them in the hospital and see if they are both okay.