Calming techniques

My 7 year old daughter often gets angry when she has to stop doing what she is enjoying to do other things. Main example: At 4:30 the girls have a light that goes on and gets brighter until 5 and that is when I go in and instruct them that it is clean-up time for the day while I cook dinner. She gets angry and if she chooses not to get calm, comes and sits in the calm down chair in the kitchen. However, in the chair she says all sorts of nasty things about herself, me, or her siblings. I often ignore what she says or remind her that it is her choice to get calm and go do her chore. Sometimes she remains mad up to dinner. After dinner she will then have to go clean her room with dad if calm or if still mad goes to bed (dad sits with her) while I do story time with the other kids. Then she wakes up calm and cleans her room. Are we missing a step? Letting her be angry too long? Any advice on how to help her calm down quicker? This happens about 1x/week.