Hello,
Yup, I've been through the, You're a faker. Attention seeker. Etc. Etc. too! It's not fun. You have nothing to back yourself up. You usually look just fine! And, you hear, "Oh, Come on. It's can't be THAT bad!" Well it CAN!
It might help to see if there is a support group nearby. I know I would be even doubting myself off and on...maybe this WAS all in my head...Others going through the same thoughts and feelings and PAIN and exhaustion and fog...and...and...AND will help her through the tough times. Because, there will be some very tough times with your sweet daughter looking like there is absolutely NOTHING wrong with her, at all!

Just tell your sister to....Well no, that wouldn't be nice. But you could tell her to Google it. There are so many invisible illnesses or conditions out there now: Autism, mental illness like manic depression, cancer, heart disease, our families all have something. You would think we would be kinder to people close to us who need our understanding. There will be times, however, that feeling like a pile of wet grimy newspaper or not your daughter will have to get on with life and "Do it anyway." She still will have to learn how to carry on through the times when she must show up for herself until she is able to let everything go but what she can manage at the time.

And you, Dear loving Mom, as minnesota10 said, you take care of yourself...It's the "Put the mask on yourself first rule" ya know? And try to keep things as light as you can about it with her. I have a couple of friends and my sons who can kid me (they know when and when NOT to) about sleeping in the afternoon or was my head on straight today...so that I know I am still "Okay."