There is no designated drop off/pick up zone. You could drop off via any entrance to the parking lot. However, pick up could be tricky due to traffic. I would recommend planning somewhere to meet her so you don't have to reenter the parking lot area at pick up.
You VIP, if so try Gate 5
Security is all over the place and quite helpful at Riverbend. Zoom in on a satellite view of the parking lots, venue, and surrounding area. The handicapped parking area right outside the main entrance probably is what I would use as a drop off and pick up spot. It's well-lit with both security and ticketing/usher personnel within easy and near access if she needed help.
You should be able to get in any of the gates to drop off and pick up. Or at the very front of the building and they could walk to an entrance, which wouldn't be far from there
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