While I would ALWAYS support trying a ride before you decide you hate it (especially Big Thunder and Splash, because they are relatively tame), your wife should have no trouble using chicken doors on those rides.
Just make sure that she decides that she doesn't want to ride BEFORE you enter the ride vehicle. I've seen it twice on ToT and Soarin' that people get strapped in and then panic because they don't want to ride it. Castmembers aren't nearly as understanding at this point as they are before you are assigned your row.
As I said above, I really think that your wife should try these rides, not skip them. But don't force her
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Everest is a fun rollercoaster, very tame, not rough at all. I am afraid of big rollercoasters and have never had trouble on Everest.
Rock n' Rollercoaster is a good one for chicken doors, because she will get to see the launch before she gets to the grouper. It will be easy for her to decide if the ride is for her or not. In fact, she'll probably meet a crowd at the chicken door who have made the same decision as her.
Tower of Terror is super fun, but if she's really afraid of heights or hates the feeling of falling, she really shouldn't ride. My mother hates both and was scared to death on ToT. If those don't bug her, then she should probably give it a go.
Big Thunder Mountain and Space Mountain are not big or intense roller coasters at all, but they are old, so they are rougher. I know Space Mountain REALLY throws you around, especially when you sit near the back. Gave me whiplash last time :/
Splash, the only intense moment is the big drop, and it only lasts a little while. Go for it!
The chicken doors are all easy to reach for these rides, just explain to the castmember when you reach the front of the line.
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