fickle

(s) marked by erratic changeableness in affections or attachments
- fickle friends
- a flirt's volatile affections
volatile,
(s) liable to sudden unpredictable change
- erratic behavior
- fickle weather
- mercurial twists of temperament
- a quicksilver character, cool and willful at one moment, utterly fragile the next
erratic, mercurial, quicksilver,

volatile erratic mercurial quicksilver

fickleness