Well, that's quite a start for a Rookie... welcome to TFP
and thank you for being so open on your first post!
Love... well, that's interesting.
I've been with ktspktsp (my SO) for 2.5 years now, and we're getting married in less than 2 weeks. And yet I don't know if I could define "love" any better today than I could before I met him... in fact, I think all of my ideas of love have been transformed by virtue of being in our relationship. And I am okay with that... more and moreso, each day. I don't need many definitions anymore.
Love exists, and for that I am grateful. It is not the same love as when we started out (we were younger), but it has matured with us and grown us into better, healthier people... and that is how I know it is real, for me at least. It has seen us through some of our ugliest sides and moments, and I know it will see us through many more of those to come... and I am not afraid anymore, of anything we will face together.
But, if pressed, I would have to answer your question by asking you more questions:
--Why do you think she is "perfect?"
--Are you willing to be responsible for her well-being, even at the cost of your own desires?
--Have you ever used the word love before, with anyone else?
--Why do you think that you both have not used the word "love" with each other before?
--Do you need to know what love is, in order to experience it and know it is true?
--Why did the conversation end prematurely?
--Why did you hesitate to answer her?
I also just want to say... it's okay to not be ready for marriage yet. In fact, it's more honest to be at that point, than to be uber-excited about it externally, but nervous and insecure internally. If she is the person that you are truly going to walk through life together with, the marriage-readiness will come on its own. There is no forcing it. You will, actually, know when it is time. And it's not now. But that doesn't mean it won't be ever.
A bit rambly, but I hope this has been helpful. Certainly good for me to write it.