Ignorance is Bliss!
We all are social animals, everyone needs attention be it from one, some, many, all.
When you don't get attention from the person you want, it feels like ignored
But the point is it's an individual choice to give attention or not, so let them do whatever they want and don't take things so seriously!
Human is by default selfish and has ego. Being ignored is like hurting Ego, many can't handle rejection.
It's not always the way we want so stop displaying destructive emotions and indulge in other stuff which gives excitement
In the end everything changes its inevitable so enjoy with whatever you can rather than overthinking about something which destroys YOU.