Sounds like she panicked...I'd like to hear from long time instructors if people that have panicked in the past are able to overcome their flight response through more training, or hear about their experiences with divers overcoming the urge to flee when panicked.
I think it's both skills practice and also an imbalance between skill levels of buddies puts added pressure on the less comfy buddy. Usually self-inflicted pressure as the buddy who also happens to be the husband seems very supportive and just happy to be diving together with his less comfy wife.
My husband and I went through the certification steps together, but we have a pretty different diving personalities - he was comfortable from the start, and I was super cautious and pretty nervous. Weird because I love to swim and he hates it. The end result of this is that he's advanced quicker than I in underwater comfort/skills. We've sorted out the buddying and I don't dive without him, although he will go for deeper dives with instabuddies.
First point: The difference in our comfort levels resulted in a pretty deep discussion, the bottom line of which is I AM RESPONSIBLE FOR MYSELF, THEN MY BUDDY ... and HE IS RESPONSIBLE FOR HIMSELF, AND THEN HIS BUDDY. This was actually quite freeing - finally getting, *really* getting, this concept that I have responsibility for myself and I am NOT dependent UNLESS I get into an issue then it's expected that he, as my buddy, will support. And vice-versa, which has happened as on the first couple of dives on our vacations he is an absolute air hog and I never am. We love to dive together, when we dive together it is to my comfort level, and I look forward to many more decades under water with my dude.
Second point: On about half of my first 10 open water dives, down to hard bottom no more than 40 feet in the big Caribbean sea, I would look up and go 'holy ****' and start to panic. I actually bailed on one dive from 40 to the surface with no safety stop...felt like a tool later, but at that moment I HAD to be on the surface, stat. Didn't care about my buddy, notifying DM, anything but breaking the surface. Over the course of the next few dives, it became apparent I was laying down a pattern. Descend, achieve neutral buoyancy, all good, this is awesome, then about 10 minutes in, 'what the heck am I doing here? anxiety'. Look around for my buddy and cling. Then we had the talk of first point above. Then I started to seriously work through this because I really LOVE to dive.
I started practicing skills more on dives with my buddy. I took responsibility for myself and stopped going along with a dive that I thought might be too much for me on that day. I have sat out a couple of dives so far that sounded like they would be too challenging for my comfort level.
On my 12th dive my reg came out of my mouth at around 45' - have no clue how. I glanced at my buddy who was at that exact moment looking the other way, did the one arm sweep, tongued it, purged, and hey presto - I had air. Muscle memory and practice. Zero panic.
Having said all that - I've never had an actual freeflow issue which must be scary because of noise and bubbles. I've also never had to do a CESA in real life. But although these totally freaked me out in the open water tests, I made the instructor sit there while I did it over and over and over again. Moi OCD over stuff like this. I still practice these occasionally in shallow dives or ascents after safety stop with my buddy. If it is freaking you out, it is an opportunity to practice the skills to deal if it becomes a real life need.