All I can say is, you'll still have those feelings even in a long-term after 15 years together. It's the "grass is always greener" kinda thinking. You're feelings aren't invalid, but the expectations sometimes doesn't come from reality and instead from media. We have such a screwed up view of what a relationship is "supposed to be" because of the shows and conversations we consume. Try to avoid romcoms/etc while getting your head cleared up a bit (anime's are also bad about unrealistic relationship expectations).
The reality is you're just two people trying to learn how to live together (either online or off), just be open and communicate properly. Saying, "Hey, I've been falling behind on my responsibilities and I have to focus on some stuff for the next few days" probably would've been a good heads up. She might've went to the party to distract herself from wanting to hear from you, maybe a response from not hearing from you, or maybe it's something completely different and just wanting to experience life. Just work on communicating and excepting feedback/learning their position. That will go forward with you regardless of any outcome and will be a way to work on things.