Seriously, welcome to living together. If you want to do it successfully welcome to the world of compromise. You started with a good issue because there are a lot of learning points with it. lol.
First lesson, You don't read minds. Neither does she. You "should have known" needs to stop now. For both of you. When you have a problem, you need to put it into words to let the other person know.
Second lesson, what bothers one person can seem normal to the other. And vice versa. She's let you know that she'd like you to get up with her. You need to get to the bottom of why, of what she expects to happen when you are up in the morning so you know the best way to respond.
Maybe the morning is her most relaxed time and she'd like to spend some of that with you. Then getting up could lead to more talk and closeness in your relationship. Or you could make an effort to make another time of day equally relaxing.
Maybe she feels like you are lazy sleeping in. In that case logging work hours and recreation hours for a week could help. Or pointing out that she goes to bed earlier than you and gets her extra rest then.
Maybe she is rushed in the morning and thinks that having you up to take on some of the morning chores would help. In which case you could be supportive by getting up or by working with her to streamline the morning chores.
Like I said, there could be a number of reasons she would like you to be up. And there could be an equal number of ways to deal with the issue. If you talk together you can discover what the heart of the matter is and work together to find a compromise that works for BOTH of you.
Even if you do start getting up, maybe you don't have to do it every day. Maybe you get up 2 days a week and make sure she has 2 days (or whatever her days off are) to sleep in too. Or you get up and then go back to bed after she leaves for work. But the better you learn to work problems like these out now the longer and happier your relationship will be.