VBACs are harder to get these days... but that also has a lot to do with where you live and how open the OBs in your area are to VBAC moms. Around here, you have to go to a midwife to attempt a VBAC because none of the OBs will touch it (which is completely
insane, IMO.)
ICAN is a fabulous site
http://www.ican-online.org/ Lots of Great information!
A great book is
The VBAC Companion by Diana Korte.
Probably
the most important thing, is to have a Truly supportive doctor. I've heard (online as well as in real life) Way too many times of doctors seeming to be supportive in the beginning of the pregnancy, but then starting to waffle as the pregnancy goes on... and ending up just flat out telling the mom that she shouldn't/can't attempt the VBAC because the baby's too big, her pelvis is too small, the chance of rupture, blah blah blah.
You may have to find out who your sister's doctor is (if you're in the same town) and switch caregivers...
Also make Sure your previous c-section was done with all the cuts horizontal... One of my LLL moms had a c-section with her first, wanted to attempt a VBAC, switched doctors to make that a reality... but when her new doctor looked at her file, told her that her previous doctor, for some unknown reason, had done a Vertical cut on the uterus itself (even though the cut on the skin had been horizontal). So, she had a planned c-section with her 2nd baby.
I know my post is sounding rather negative, but unfortunately it's getting harder & harder for moms to be Able to attempt a VBAC in this lawsuit-happy-doctors-afraid-of-malpractice day & age. You have to do your homework and Work for that VBAC.