Relationship I triggered my girlfriends trauma and she left me a week later

Ending this relationship has left you feeling confused and guilty.
Putting everything you've written to one side, it seems this was a genuine accident that can happen to us all.
Your former partner has taken this very seriously and there's no chance of reconciliation.
Your ex blames a former boyfriend, yet it's likely to have been something much deeper.
There's a possibility that the trauma caused by the ex-boyfriend will have been a very similar incident to yours.
However. The origin of your ex-girlfriend's problems may have been created a long time ago.
The result is her not being able to fully face and accept this.
Sadly - your former girlfriend may be trapped in a continuous cycle of forming new relationships, gaining trust and then following on with something similar to your experience.
The events of your former girlfriend's past could still be haunting her and she has never found any resolve.
Your ex-girlfriend's buried past experiences rise to haunt her again so she needs to end that relationship.
Although your ex-girlfriend mentioned this negative experience about anal sex with a previous partner, this may be connected to an experience prior to that relationship.
The origins of her problem will have come from a much earlier time in her life.
It will be very difficult for her because it is having an impact on any new relationships - yet at the same time it has been a distressing experience for you.
Unfortunately, due to your partner ending the relationship, the only thing you can do is accept that it's over.
The sexual event that ended your relationship was the result of misunderstanding on your part.
Sadly. Your former partner will move on to a new relationship and this is likely to happen again. There are some issues here that she needs to address - and that's a decision for her to make.
All you can do is look forward, put it all down to experience and move on.