Usually to blow out a white background I put two strobe heads on either side of it and set them to 1/2 to 2/3rds fstop over the main light. That is enought to usually blow out the background. Here is a typical light setup for this:
and here is a shot with this lighting setup and the model in white:
I was 1/2 stop over the main for the background light.
By the way it looks like you have a color cast to the photo.
Cheers,
rfs