Where I have trouble on Expedition Everest is going backwards. It goes backwards for much longer than I expect and I have watched the videos and timed them and have ridden twice, and still can't get used to it. When it gets to the bottom of the backwards part the g-forces are strong enough to make me feel like my stomach is going into my throat. Before I have time to recover we are going down the 80 foot drop that then swings around in a curve where there also heavy g-forces. I have been on EE twice and both times I have been so out of it that I have no recollection of the forwards 80 drop, and memories of hyperventilating and numb fingers and toes a the end of the ride.
Rockin' also has heavy g-forces at the end of the launch that actually make me start to grey out and make me a big high for the rest of the ride, but after the launch Rockin' is very tolerable for me, and Test Track also has heavy g-forces but are not as bad as the other two mentioned.
I'm explaining all of this only because motion sickness is enough to deal with but when a person might be anxious about how motion sick they might get on a ride, they might already be hyperventilating and that would exaggerate the sensations of the g-forces on EE.
I don't think there is a huge motion sickness problem on EE but some people may struggle with a fear of heights, and the g-forces and the motion sickness might not even be an issue but still could ruin a person's next few hours if that's not their thing.
I'm still trying to get my guts up to ride a third time. Neither my husband or I have gotten used to Everest and we were thrill ride junkies as kids, riding most of the major rollercoasters in So. CA in the 80's i.e. Viper, Montezuma's Revenge, etc, and we just haven't been able to embrace EE. Rockin'? No problem. I'll ride it again and my hubby has ridden it many times but won't go on EE, so that should give you an idea as to whether it is wise or not. Maybe have her do EE at the end of the day so she can try it once and see?