I used to get defensive about VS since I worked there and I thought I did a damn good job at measuring, but I've come to realize that a lot of the problems come from the bras themselves and what the mainstream market has caused consumers to believe about bra sizes. When VS can't get that right, no wonder it's impossible to get a consistent size there!
If there are any redditors out there, I HIGHLY recommend /r/abrathatfits (
http://www.reddit.com/r/ABraThatFits/) especially their "starter guide":
http://www.reddit.com/r/ABraThatFits/wiki/quick
The problem is there are quite a few misconceptions about bra sizes--for example, so women believe that if they are "smaller" they are automatically a A or B when that's absolutely not true.
I followed the instructions on the link above to find my fit--I came up with 30G!!!!!!!! I had been wearing a 34D!!!!! I was in disbelief because of those misconceptions led me to believe that someone like me who didn't look "busty" could no way be that size. So a week later I went to Dillards (one of the recommended stores for true bra sizing) and she came up with 30DDD, which is what I told was comparable to 30G and OMG it fit WONDERFULLY. One big mistake I was making was I was worried about "back fat". Yes, my 30 band is snug, but is correct and with my shirt on, everything looks SO much better than the 34 band I was wearing.
So basically, stores like VS are extremely limited to "traditional" bra sizes when in reality, 34A-38DD sizing misses out on a LOT of women.
I highly recommend going to Nordstrom or Dillards to get a real fitting. Try the self fit guide that's linked in those links above too--you'll be surprised, but trust me, it's correct (and if it's not, it will be SO much closed than what VS is telling you).
/brarant