Hello there and welcome
We have a few other members here who are friends or family members. Your friend is obviously very dear to you if you want to find out more about the condition.
Your question about how to help her is very vast but on the whole, we simply appreciate people being around and giving a helping hand when they can (without having to ask for it). Understanding that someone may not be able to do certain things and may be very easily tired is also very important. It is often possible to continue doing a lot of fun things but it takes a little thought to make it easier; for example, going out in an evening might be quite difficult but having a nice evening with friends and DVDs can be greatly appreciated.
You need to know too that sometimes your friend might seem to push you away. Generally it is not that at all but if someone with lupus is flaring quite badly they will often only have the energy for themselves and literally won't be able to cope with being sociable. Although it is important to respect that it is equally important that that person doesn't feel abandoned by her friends. Being diagnosed with and living with a chronic disease can be a very lonely business at times.
When she is ready for that your friend might also find great comfort and a lot of information on this site, so if she hasn't already come here, maybe introuduce her to the site.
just a very brief answer, hope it helps,
Katharine