If nothing serious has happened I bet she's sat there with her crunky snacks catching up with Tattle and absolutely loving all this speculation. She will come back as if nothing has happened and it will be just same tit different day.
I just can't think of any other reason why she's lurking in the background of Instagram and not posting.
I've gone through so much stuff in my lifetime, bereavements, mental health issues etc. And not once did I open my apps and go on social media. Infact during these periods it's been to the point where I've stayed off it completely. Even deleted the apps at one point. I've needed breaks to come to terms with the things going on in my life.
Never have I at any point lurked whilst following/unfollowing people. I even ignored my message notifications. So why is she playing this silly game? Is it all for shits and giggles?