fickle
FIK-uladjMeaning changing loyalties or feelings often
Memory hook a FICKLE NICKEL: flips like a coin. Ivy picks her best friend by flipping a nickel: heads it’s Zoe, tails it’s Lila, and tomorrow she flips again. Loyalty that flips like a coin is fickle.
The fickle cat loved me on Monday and ignored me by Tuesday.
In context Fans can be fickle: they cheered the young pitcher all spring, then booed him the moment he lost two games in a row.
Similar changeable, inconstant, unreliable, capricious
Opposite loyal, faithful, constant
From Old English ficol, “deceitful, crafty.”