Your not being a horrible friend. But you might be taking this too personally.

If shes not getting enough sleep and such thinking clearly might be an issue. Also maybe she's thinking that if you have problems with being tired all the time then mayb you can relate.

I can say you can speak up and tell her to stop it. And she would probably stop, but she might just stop talking to you all together.

You might want to take a look at how much you complain to her and see if that's why she thinks its okay. If you both tend to complain about things with each other maybe she doesn't know that this particular thing is diffrent to you because it annoys you because you are tired also.