If you can't say it do something sweet for her that she will always remember. Gifts don't express love, and as someone else said sometimes words mean jack shit especially if you will struggle saying "I Love You". She will see that and doubt it. Think of something that will make her realise what she means to you. Something special. A hot air balloon if you can afford it or a picnic down by a water fall...something along those lines
There is no need for temples, no need for complicated philosophies. My brain and my heart are my temples; my philosophy is kindness.
Dalai Lama