vacillate

动词 vacillate:

1. be undecided about something; waver between conflicting positions or courses of action
   同义词：hover, vibrate, oscillate
2. move or sway in a rising and falling or wavelike pattern
   同义词：fluctuate, waver

1. She vacillated between hope and fear.
   她时而抱有希望，时而心存恐惧。