I hope you read the basics about lupus. Generally speaking, it is chronic disease so we are expected to live about a normal life. We just are going to have some bumps along the way. So, just read only recent like in the last 10 years worth of articles on lupus and you should get a very clear, honest picture about it.
Right now, she is going through, what i call the grieving stage. As you know, due to your life's experiences, you must grieve to keep moving on when bad things happen. This is going to be large upset and worry for her until she can understand how the lupus is going to affect her life.
That is 2nd emotions she will be having along with grieving. Worrying about every thing that now occurs is it the 'lupus' or not. You can really help her in this area as much as with the grieving by helping her to try and realize exactly what is the lupus and what is just getting sick same as normal person would. There is always the 3rd option, that something else is going on as well. So it gets very confusing for us and takes on average a good year or two to figure this out.
Mainly, if she is feeling very tired where she starting to feel sick, she needs to start resting. If she can learn to try and listen to her body and rest this will help her greatly. But most of us, will push it just because it can feel like we need to rest for months. Or once a flare pops up which is what we call when we get sick...if you keep pushing it too hard, it will just keep lasting all that much longer. So resting is very important...even more so than getting scared and running to doctor every time you flare.
She should ask her doctor about what warning signs she should look for...and it help if you know them as well. This way if she is not well, you can help her determine if it time to go see a doctor or not. Her doctor should be able to help her know when it is time to worry and see them and when give it time and rest. A good part of this is just her getting to know her limits as well.
But here is the very good news, they are making big strides in lupus and all autoimmune diseases. I have read repeatedly that they expect to either have cure or much better life for us for those as young adults now. So she should have good life and hopefully find a cure in her lifetime!
I will add, that i totally can understand how close and worried you both must be. I was very close to my older brother. He was 22 months older than I and always had been sick all his life. This was in 60's on, he was born in 1952. They never knew what was wrong with him and he was put through a lot of horrible tests and tortures as child and young adult. I was sick, i realize now more than my friends but i did not think of myself as sick compared to my brother. I found out i had lupus in my twenties so was early 80's. He died when he was 34. They now are using drugs commonly that i tried to get his doctors to try on him, but they were in experimental stages and i think my brother just was in too much pain and tired from it all. He found love and had children. Something he thought he never would have before he died. He really pushed himself to make sure they had nice life though his daughters were only 3 and 5 when he passed. I am positive that he died partially from pushing his body so hard. I am now closer to his level of illness and i really wonder how he managed to work full time feeling so poorly. So you might hear of some people passing from lupus, these are rare cases, most of us do live long lives...maybe hurt and feel tired but should be fairly happy lives.
OH...one thing i have noticed is your self out look on it. If you feel you are going to continue to have happy life, yes you are going to have off days and not feel well but those people tend to do better. They handle pain much better in all studies and even the fatigue. So make sure she does things she enjoys!! I even noticed i can be in great pain but if it something i love, pain is worth it...where if at work...i get exhausted from it. Hope that makes sense.
But i wish you both the best...you both have been through enough.