RK7

Also you make a will and list her as your heir.   You can also to a medical power of attorney.

Relax.  Many of us married someone outside of the USA.  They know that you can’t have joint property.
 
RTLE outlines good items.  
 
Pictures together and you with family are good.  A couple from each meeting if you’ve met several times.  Like chats, don’t overdo it. 100 pictures at your wedding is still just the same day.  A couple from each trip is plenty.
 
If you add her to your retirement plan or as a beneficiary, it can help.  Only if you happen to work for a company offering that.
 
 

face-time meetings are the primary evidences: Copy of passport stamps, ticket/e-ticket Pictures of your visits, including you two, and you with her family members, and she with your family members Receipts for gifts and stuff you two sent each other Phone logs, video chat logs, chat logs Do not load them with hundred or thousand pages - just a few pages should be good enough  
Some people tend to load with joint financial stuff but personally, I do not think these carry much weight when Two are newly wedded Two live separately in two different countries Because the beneficiary cannot really use these financial resources while she/he does not live in US  and petitioner still has total control over these stuff but examples may include
Add beneficiary to petitioner's credit account Open a joint account Place beneficiary's name on retirement account/life insurance account.

List down all the times you went to visit her throughout your relationship and provide proof (passport stamps/ flight ticket / pictures together from the visits) - this was pretty much the only evidence I sent with my application. 
 
Video/ call record to show  communication.
 
I don’t think your K-1 termination / expiry letter would cause any issues but I’m not also not well versed with that. 
Good luck.