Absence of evidence is not evidence of absence.
We know she was taking to him as Magi-Chan and telling him to do things like taser people to trigger the merge. We know she gets off on manipulating him, along with rape and incest. We know she was the only person he'd tell who his new sweetheart was (he wouldn't even tell Null), and that she was able to "guess" from very minor clues. We also know she doctors texts, enjoys telling people lurid fake details of Chris/Barb BDSM because she gets off on it, and that the entire unrelased call was 4 hours and we've only heard like a half hour of it tops. We also know she was extorting Chris for financial and personal gain, and planned to extort/influence him into killing himself and possibly Barb too, and she was mad that Fiona leaked the call, and faked a call to 911 to stop Fiona contacting the authorities.
We don't have evidence she did it, but we certainly don't KNOW that she didn't do it.