In the closet relationship

So I’m 15 and I have a girlfriend and I’m still in the closet. People say you should wait until you know you’re 100% safe to tell your parents and so I know I can’t do it yet. Things are starting to become difficult in the relationship because I’ll be on FaceTime to my girlfriend and my sister will ask who it is and I have to say just a friend and I know that hurts both of us for me to have to say it. It’s just really frustrating how straight people can walk home and say they have a boyfriend and everyone will be happy and want to meet them yet when you’re gay it’s still seen as not normal.