My younger DD (also 7 and in 2nd grade) struggles with reading comprehension as well. She can understand and relate to books well beyond her grade level if she listens to them, but often can't answer even simple questions about the story if it's something she's read. DD has problems with tracking, tends to read too fast and miss words, and sometimes focuses more on the pattern the words make on the page than on the words themselves.
She enjoys crafts, so we made a bunch of bookmarks for her. Like aculady's DS, she puts them under the line of text she's currently reading. It slows her down and keeps her focused on that part of the page. I don't know if it would help your DD, but it might be worth a try.
