I am really sorry to hear of your sisters suffering and the lack of help she is recieving. You will find many of us on this board have been, or still are, in the same situation. I cannot offer any advice regarding Insurance and doctors where you live as I am from the UK and our system here is different, but there are many people here who will give you lots of help in that area.
You say she has a diagnosis of Vasovagel Syncope, was this diagnosed through a tilt table test? What medication is, or has, she taken for this? Common ones would be Florinef, Midorine, Paroxitine, or a betablocker to try and help with the 'overshoot' that causes bp to drop.
If she had a Tilt Table Test what happened to her heart rate?
Does she have problems with her heart rate, does she ever experience a fast heart rate? What happens to her heartrate when she stands?
What tests have been carried out?
Many people who suffer with a form of Dysautonomia are often told they are fine!!! This causes them added stress and suffering.
I am sorry for asking all the questions but I am just trying to get a bigger picture of what is happening to your sister. The community leaders on here are great they will help you, but they are not so good themselves so it may take them a little longer to reply here.
Below is a link to the health pages of this community, have a little look on them and see if anything sounds familiar to you and your sister.
http://www.medhelp.org/health_pages/list?cid=196