The first part...regarding the accident: That isn't OCD. That's PTSD. I advise talking to your pediatrician and perhaps a pediatric psychiatrist/counselor.
Second, regarding her tics and interests...many children develop little tics like those you've mentioned. They usually get over them as they grow. My boys both occasionally bite/suck on their bottom lip. My oldest will stretch his neck over and over. They usually don't realize they're doing it at all...but I've found that a reminder helps. Eventually they stop doing it altogether. My ex's son used to rub his nose, eyes and mouth over and over. It'd get worse if he was stressed.
I J. reread...hand flicking? It's sounding more and more like your child might have mild Asperger's. My ex's son has this (I researched it and diagnosed it). Perhaps you might consider researching this very high functioning form of autism? Aspies tend to be highly sensitive, highly intelligent children who learn and grasp the world in a unique way. If this is your daughter, you'll need to learn about it so you can teach her coping mechanisms which will help her to succeed in school learning environments and social situations.
Interests are going to seem obsessive...of COURSE her "flavor of the month" will be the topic of all her conversations. Common for Aspies are intense interests in planes, trains, space, dinosaurs, weather, disasters, death, cars, military, history, antiques, and more. That's okay because her brain NEEDS to learn. And if she loves it...give her more on the topic so she can focus on those things, but you'll need to help her learn to control herself and recognize when those she's "lecturing" are getting bored. Aspies tend to be socially awkward and dominate conversations.
I hope this helps a little...it's J. the tip of the iceberg. Asperger's is a highly complex condition and needs lots of research and time to fully understand and diagnose. She might not have it at all...but from what you're telling M., that's what I'm thinking.
ETA: Oh...and my ex (the little boy's father) is an Aspie too. As is his father. Three generations of Aspies. ;-)
In response to your "So What Happened," Aspies are all different. Some might exhibit some behaviors more strongly than others...or not at all. It's a spectrum disorder...not all symptoms may be there. Aspies cannot usually be definitively diagnosed until age 8 or so.
Finally...it might be that she's gifted. Perhaps you might consider having her tested? Gifted kids, like aspies, can sometimes have some strange little quirks. ;o) I know I did/do.