I agree with the replies here, you are an awesome sister and a great person for actively seeking ways to help her.
I also agree with all of the points made, especially about the time of mourning for our old lives. I know that I have hurt myself trying to push myself to limits I used to be able to easily meet, but I had to go through that. If I'd had people forcing their help on me I might have become bitter, still believing that "If people would only let me...". The eventual result is that now I am becoming better about admitting when something I used to be able to do with ease is a little out of my reach, and because I have had wonderful people, like yourself, who have never judged me, I am getting much better about asking for help. We even joke now, using that line from Analyze That "It's a process."
Education is awesome. It's important for you to know, though, that fibromyalgia is a complicated thing, and it seems that no two people have it quite the same. There are a ton of similarities, though. You could broach a conversation with her about which of the symptoms she has.
Be careful about offering "cures". I had one friend who, while she was well meaning, told me so many times that if I went gluten free I wouldn't ever have another symptom that I stopped talking to her for a bit. I had told her that I tried it, and she told me I must have cheated. Sometimes people get so excited about what worked for them that they assume that if it doesn't work for you that you must have done it wrong.
Definitely keep an eye on her to monitor for depression. A lot of us suffer in silence because we don't want to burden our loved ones, even when they say and show that they are willingly to go on our new journey with us. Don't be too insistent, sometimes we just have to cry it out, but keep it in mind.
Offer to do things with her that she might like, and if she cancels on you, offer her a low-energy alternative. Instead of going for the planned walk, offer to come over and play a game, or even watch TV and chat. Be forgiving with her about being late to things, as much as is possible, but don't cut her a mile of slack all the time, especially after a few months. Sometimes it takes extra time to curl our hair, or get out the door, especially when it's all so new, but I found that, with my super-forgiving friends, I was starting to take it for granted, and was trying a little less. I started canceling plans hours after I was supposed to show up, when people were waiting for me to start something. I was gently talked to about this, and it made me realize how selfish I was accidentally being. Now I know to cancel early on, and to always keep someone informed of how I'm feeling, just in case I need to be significantly late.
Sincerely compliment her, when it's appropriate. If she looks nice, tell her. If she cooks something tasty, let her know. Sometimes these things take a great deal more effort for us to achieve, so when we hear the benefit, we are motivated to keep going, to do it again. If we feel that no one cares, then why should we spend all that extra energy? Don't over do it, or be saccharine about it, though. No one likes to be patronized >XD
That's all I have off the top of my head, but I'll say it again. You rock!