It sounds like you have everything figured out, so I don't think there's any reason to be stressed out. It all sounds good to me.
They don't want access to your accounts, so don't worry about that. Just a few sample messages showing that you had contact long before the wedding and that there was ongoing communication leading up to it would be useful. You are the one who chooses which ones to send, so you don't have to send anything too personal. Messages discussing a possible committed relationship or possible ways you could be together would be great. The main aim is to show that there was a developing relationship and not just a quickie wedding arranged for a "marriage of convenience." I'm probably making it sound more onerous than it is, but do keep everything in case you need it.
Things like boarding passes, receipts showing travel, etc., could all be useful. If you have dates of electronic communication showing frequency of contact, that's useful too. You don't need a lot of this stuff but it's good to have some.
The long visit probably won't work for your situation, but if she wants to visit you here, a job to go back to and an apartment with rent to be paid are useful to show ties to the U.S.