Help–when I go to reply to an e-mail there is no way to reply except in the middle of the page between my e-mail and hers–what to do?

I send a message, I get a reply and then I try to reply to that; there is no place that will receive my writing except in the middle of the page,  between my initial message and her response. it was not like this before as the original messages were  not included in the page I am trying to respond on. This is hard to explain!