Pediatric RLS is tough because kids language skills are limited.
First and foremost, RLS is a movement disorder. There is a strong urge to move. That urge might not feel like anything (no sensation), it might feel icky, weird, annoying (a sensation), or painful (a sensation that hurts).
That she wants to move is probably what the doctor is keying on. That is occurs at rest is another component. Is it RLS? I don't know. It seems like it from here, but I'm not a doctor and I'm not inside her body.
Have you read this? http://www.rls.org/Document.Doc?id=347
It's a document put out by the RLS Foundation on RLS in Kids.
Here is a slide deck with info that may be hepful: http://www.rls.org/Document.Doc?id=1934
I'm not familiar with Children's in Boston. Johns Hopkins has some of the foremost adult researchers around. It might be worth called Johns Hopkins and seeing if they have a recommendations. Daniel Picchieti (maybe misspelling that) is an excellent ped RLS doctor in Illinois. He would take your phone call, I think (he's taken mine and I'm an adult!), and he might know of a good doctor for you to see. Another option is to write Dr Buchfuhrer at firstname.lastname@example.org
and ask him for a recommendation. He's in California but, like Dr Picchieti is/has been on the RLS medical advisory board and both know many other doctors.
Check out Jill Gunzel's site, the RLSrebel.com. SHe also has a book. She provides many ways to cope with RLS that do not require medication. You might find ideas to help there.
Things that may help:
Some of us like heavy weights, like a blanket, on our limbs, others hate it. Try both.
Warm bath or hot tub - this helps many of us.
Puzzles or things that distract our brains into thinking
Avoid sugar - it's doesn't work for all of us, but some of us are bothered by it and cutting it out can help a lot
No caffeinated soda or chocolate
You've already tried massage - I hate it! but, this is what makes RLS so difficult...other people love massage. It makes me squirm just thinking about it. I also hate tight clothing, tights, pantyhose, leggings,tight jeans, etc., yet other people get relief from using pantyhose. I also hate dry skin. No idea why, but some of us have a sensory issue - if the skin feels dry or tight, it starts the RLS. So keeping it hydrated can keep the sensations away. Other people never mention it.
Per the crying....when RLS is active, at least in me, it has an associated emotional state. I am anxious, agitated, and upset. I hate how it feels, I hate having to move constantly, I just want it to stop. It's like an invasion of my body. I honestly don't remember how I felt as a child...but my family had it so I had role models and knew what was going on.
Could be this is her way of sharing her distress. Could be that it isn't RLS. But, I can cry now as an adult....and I'm not 8 and not able to understand and process it.
Not sure I helped any...hopefully some others will add their ideas, too.