It's pretty obvious what's happened, you've pulled out, checked left (clear) then proceeded to pull out at the exact moment she's come along, you obviously haven't purposely driven into her and she hasn't driven into you.
Neither of you could see each other till the last minute because the van was in the way, so you've both basically gone to occupy the same space at the same time, and neither of you could see the other because the van was obscuring both your views, she had right of way though as she was fully turned out and past the front of the van at the time you hit her.
I suspect you were going quicker then you think as you pulled out, OR instead of pulling out straight to check what was there around the van, you had a quick look then drove off at an angle instead, putting her in your blind spot.. either way means you didn't look properly.
At the time of pulling out she was there approaching though, she probably assumed you would stop seeing as you didn't have right of way.
You've both made assumptions, her that you would stop and you that you were okay to pull out when you obviously couldn't see properly. But the onus is on you to check your way is clear before pulling out, if you can't see well enough then you don't just pull out and hope nothing is coming.