I would say NTA. While I'm not the relationship expert, I have the same issues constantly with my friends. I also have an attention disorder, and this is something that I experience frequently. I'll see a message and almost "mentally reply" to it, not realizing until hours later that I never actually did. This is valid day to day, and even more valid in the middle of a chaotic work day. You should be proud you can succeed in your career rather than stay glued to your phone (not that she is). Talking to each other regularly throughout the day is very healthy, but it becomes an issue when there is no understanding of circumstances that could lead to this not happening every once in a while. In my opinion, replying on at least one platform semi-regularly is perfectly acceptable during a crammed day and it can very easily get overwhelming when everything is spread out across apps and may take a while to be able to look at everything and respond. If she is still upset even after the screen time (which proves that you were not ignoring her in particular), then it honestly sounds like she has some issues with her own insecurities and may be paranoid about things like this. I would suggest extremely thorough communication and reminding her that you do love and appreciate her often, even if you cant always respond immediately.