Can I just say? Thank you guys for making the Tvtropes page I made for this the busiest page I've ever made on the site.
Anyway here are my theories:
I think the Villainess System is the creation of the Yvonne from the original otome game, offended by this... "pretender" that's wearing her face. That would explain the blackout Evie experienced at the end of the date.
As for the future Elsa looking character, it's most likely that the System gave Evie a task with no way out and so chose death before harming her beloved. As she lay dying, however, Elsa was able to perceive the System and so set out to save Evie. The only problem was: how do you beat something that's apparently unbeatable. Well, it took a lot of trial and error, and many trips to the past, but she finally cracked it, and is now ready for the real attempt.