^ The best advice here.
To sort of reiterate and interweave these thoughts I have to dispel some misinformation about INFPs. We are not these emotional beings that are easily and overwhelming moved by any degree of sentiment. We are the highest critics of emotional expression - not just anything will do. I find sentimentality and cliqued romantic gestures to be very repelling. Its like emptily going through the motions of romance and hoping this will result in actual feeling. Genuine, truthful emotions are so much more interesting and appealing. The way to acheive this is to be honest with yourself and her. A understated, matter of fact, or offhand expression of feeling in an inane situation such as washing the dishes, is so much more romantic to me than a grand declaration on a moonlit walk on the beach.
Also remember words are easy. They're easy to say and easy to take back. I'm not sure about other INFPs but I'm suspicious (well, more cautious) of the things people say - they always disguise underlying truths. My ISFP friend has a saying: "love is an action word". In other words, you can't just say it, you have to prove it in your everyday behaviour. If you love her, show that its an unselfish love and be generous with yourself. Show interest in and spend time doing the things she likes, listen to her (and remember what she says), do things to help her out without her asking etc. This isn't as showy or straight-forward as flattery and grand romantic declarations but its so much more meaningful (and much more appreciated by a INFP). Hopefully, if you do more of this she may start to feel more of a connection with you and will open herself up to you more.