Well I for one believe that love has no strings attached to it. If I love someone or they love me it is not a promise of some kind of particular outcome it's an emotional/energetic state of being for as long as it stays that way.
However, that being said, many others hear those words and suddenly are planning their future wedding. So I think it's good to be clear first about what love and in love actually mean to you. Perhaps have that conversation first? It might also be a way to see what page she is on as well.
I agree with the others, it's also important to decide which of those two (love or in love) it is as well. It takes time and experience of someone in order to properly make that assessment imho.
Good luck and enjoy the lovely feelings of joy you are experiencing with another human being
