Flying with ADHD/OCD child

Our 9-year-old daughter has not flown since she was a toddler.

My wife is taking her to Arizona soon.  She might not have a problem with flying.  One reason to be hopeful is that she loves scary roller coasters--coasters I certainly won't go on!

But, as we all know, mental health issues are not always subject to reason.  She is afraid of what she calls "mannequins," for example, but is very inconsistent on what constitutes a "mannequin."  The real mannequins in the store do not seem to bother her.  A Bugs Bunny figure at Six Flags, however, sends her screaming in fear.  But a giant devil statue at El Diablo at Six Flags doesn't phase her.

I am worried about what will happen if she gets to the boarding ramp and starts freaking out about getting on the plane.  My wife has very serious anger issues, which I suspect are related to ADHD.  I told my wife to be prepared in case there is a problem, but she was pretty dismissive of my concerns.  So she won't be prepared.  I will be at work when the plane is scheduled to leave.  I hate to think what will happen if my wife is stressed about getting on the plane on time to leave and our daughter is kicking and screaming.  Ideally, I would be able to take our daughter and my wife would go on without her.  But that won't be possible because I will be at work.  (I can't take off because I need to save time for my upcoming medical leave.)