>>9404412She has a deceptively soft butt.
Real answer: More often than not, she's hitting them right between the cheeks or as close to them as possible and not the actual hip, which gives some cushion instead of taking the pelvis directly to the head. She also pulls a little bit of it by hitting the top and middle buckles first.
It probably hurts more than you want, but unless you're dumb enough to keep your head on one of the buckles when she slams into you, there's probably very little risk of a concussion. The fact that you can see her charging towards you gives you some time to brace for it and sell accordingly.
