S.T.
My 7 year old does this when she has sinus drainage. If I were to ask her if she had drainage she would say no, but she doesn't really understand what it is. It's an automatic response, trying to clear her throat. Sometimes, she swallows funny too. Does she have allergies? You might want to try a decongestant or just have her blow her nose really hard. I wouldn't worry about it unless it persists.