If I remember correctly, Event A was not in any way caused by Barnabas's intervention in 1897.
Event A caused Event B
If Barnabas wasn't there, Dirk wouldn't have been detained by Barnabas, and therefore may have caught Jenny before Event A happened ... This must be true, because Event A certainly didnt happen in the original timeline.
But Angelique didn't cause Event A. She merely helped to undo it. Or have I forgotten something?
I think it's a bit of a stretch to think Angelique was around in the original timeline, since she was only summoned to take care of Barnabas. She was the one who reversed Event A. It makes perfect sense that Event A couldn't have happened in the original timeline. Especially since we have seen the later episodes and know how Quentin really died in the original timeline.
MB-- [spoiler]I figured someone would bring that up, but in another thread someone argued that, by the time Beth talked to Julia in 1969, history had already been changed. Therefore, her recollection of what happened had changed to include Ang.
I think that sounds pretty reasonable, and at the very least shows that we can't assume A was there based purely on Beth's recollection...