Why did my friendship with her suddenly turn cold and distant?

i always got along really well with her but things seem to have gone sour all of a sudden. we never like dated so our friendship was sort of different due to the age difference but our friendship seemed genuine. i haven't seen her at all this week and only saw her once last week and we didn't really talk much , mostly she just played with her phone and pretended to be busy when nearby

Updates
4 mo
saw her briefly yesterday , she arrived at place where i'd often see her but just as i was leaving , she said hi and appeared to be in a better mood but didn't have time to talk or did i really try as i was leaving. so will see what she says when i see her next
Why did my friendship with her suddenly turn cold and distant?
Post Opinion