Like the first reply said, you possibly need to reassure her. Being single for seven whole damn years when you are only twenty-five is a huge deal - she has obviously been burnt in the past and has never recovered. It is up to you to decide whether you have the patience to try and win her over, whether she is worth the effort, and whether you are able to in fact help her come to terms with whatever heartbreak she has suffered.
However, at the same time, she may very well get annoyed if you continue to persevere when she has clearly stated how she feels about you, if she has said you are 'too good friends' then you should back off and let her breathe, don't push it otherwise you will lose her friendship too. Maybe you should become a little more reserved, retract your friendship, don't be around so much - this may do wonders for you as she may start to miss your company and realise how much she does in fact like you. It's not guaranteed to work but it's a suggestion nevertheless.
[SIGPIC][/SIGPIC]
Love is like a merry-go-round: you get all dizzy, and then you feel sick!