A couple of small tricks that I use in lines: I am always the first member of our party to enter the line. That way, I control how much we move up and I maintain a healthy space between me and the party in front of me. The family members behind me are cognizant of the issue and maintain space behind me as well. Could you just hold up before the tunnel and not enter it until she can walk straight through?
The fan and the xanex are good thoughts. I actually carry an emergency xanex in my purse after an incident on Indiana Jones (vehicles same as Dinosaur), where it broke down and we were left strapped in the vehicle for over 30 minutes before being evacuated.
They sent a young CM to our vehicle to see if everyone was ok. I answered no, I was not ok and requested that I be released due to claustrophobia (and it was perfectly safe to do so, given our location within the ride -- we were basically in an industrial building once the lights came on.). The CM delayed, went to talk to someone else, and then came back and said he could not do it but his supervisor told him to stand next to me, which made things way worse. Even others in the vehicle could tell I was in trouble and kept telling him to release me and they would all stay strapped in. I can still feel the color draining out of my face.
It came down to me either making a scene (which I decided against due to the young children in the vehicle) or employing some serious lamaze breathing to avoid a full fledge panic attack. I told the CM that if he wasn't going to release the seat belt, to please step away from the vehicle (for some reason, I couldn't shut down enough knowing that he was standing right there able to release me, but not doing it). My sister was hilarious (now it's funny -- then, not so much) telling him "no, she means it. Step away". I think she was afraid I might grab him by the throat and I can't say that it was out of the question. When we were finally evacuated, we gave away the fastpasses we were given and left the park, as I was spent for the day.
To this day, my enjoyment of disney has been negatively affected by this experience. It made me keenly aware that I am at the mercy of the equipment and staff. I never had that fear in the 40 plus years I had been going to Disney parks.
