One thing I want to point out since some timelines believe Fiona didn't meet Bella (or Chris) until this month, keep in mind Chris decided to go to Everfree in June.
We've all but established that Fiona was his reason for going in the first place, so Fiona and Chris have been in contact since June.
So, it IS possible that Fiona has known Chris since June, and Bella found her through Chris this month when he "introduced" them to each other....BUT, I feel this is not the case and that Bella urged Fiona to contact him originally, and it was part of Bella's troll operation.
My main reason for this that I've just noticed, is that the way Fiona and Bella communicate (through texting, of all things?) is way too personal and familiar for some Internet teen randos that just met a week ago. They've been talking for a while.