Not had the same experience, but I guess I might know a little about trauma.
You're probably doing a good thing by talking about it - it's not a good think to talk about all trauma's publicly, but in this case it should help to make the trauma external, especially from the safety of an anonymous ID.
There's no rational reason why you should feel shite for going ahead with the punt. Nothing you could have done different that would have made things any better for your colleage. This must be obvious to you, but maybe it helps for someone else to say it.
There was probably a collection doing the office rounds after the accident. If you was away or missed it for any other reason, maybe ask for a way to get in touch with her or her husband and say you've been thinking about them, and would it help if you sent a wee gift, is there anything they need? As they don't know you that well they'll probably say no,but 99% likely they will appreciate the gesture, and should make you feel better too.
Like others, I'd not expect this to be the long lasting sort of trauma - if you take a bit of extra care to ensure you book a good SP, your next punt should be fine. Maybe chose whatever sort of punt is most likely to make you come, or which you're more relaxed with, whether that's massage/HE , FS or whatever.
Happy punting!