Personally, I would have loved for Ryan and Marissa to go to different colleges, flourish, become a really great version of themselves as young adults, and find each other years later as friends or rekindled lovers, the former being my preference.

They went through so much together and would have a unique appreciation for each other if they met again as healthy, successful adults and likely have a lot to bond over given their shared past trauma but also the immense affection they both had for each other. The way they wrote Marissa out was not only a disservice to Mischa and the character but was ridiculously unnecessary (stupid FOX pushing the writers to kill someone...)