How am I supposed to react to my baby's back arching?

My baby will be one year old on Sunday...she's been arching her back since she was ten months old and having a tantrum...how am I supossed to react? Like say if I'm changing her diaper, should I just ignore her and keep changing it? Or be firm with her and tell her no? Or should I just put her down and leave her alone, then come back a few minutes later? I don't know if that will work though I think she will still get mad a few minutes later. Distraction doesn't work on her either...any advice? This is SO frustrating, and I thought this stuff didn't start til she was 2. Ugh.