Actually, I don't think it's a bad word to dance happily, but it's also normal, because I think that although Kubinashi's opening phrase is a situation to show happiness, you should know that if you dance, your hands are there and your feet are moving, which means you are very excited. Happiness itself is happiness. However, if you are happy, one is to actively use words, and the other is a word of that activity. So these two words have different meanings and actually use different words, so this sentence is naturally not a sick sentence.