my crush went home sick and I'm really worried?

I liked a girl for the past 2 years now (I'm a girl ) . We are really good friends but today she went home sick from school . Me and my friend brought her to the nurse and when we came back to get her she was crying because her stomach hurted bad . I feel so bad and I miss her so much . I'm used her being around all day she that's why I miss her so much how to not worry about her so much ?