It's probably admissable, since it's your MIL's computer and you have her consent. As Allen said, however, not sure how useful it will be, but I would certainly capture EVERYTHING, and then let your atty decide. Judges, after all, are only human, and there is an overall "halo effect," or "preponderence of the evidence" thing that takes place, and if OVERALL, you -- with your daily journal, notes, receipts, bank statements, screen shots, etc., etc., etc., come across as the more credible party, that will certainly work in your favor.
