Did she say it like.. "omg, Jeffersong. Thanks for bringing food. I love you!" If it went something like that, I think she was just happy you brought food.
I don't think the speed at which someone says "I love you" is very significant. Maybe she's very smart, knows exactly what she wants, and you're it. Having someone love you is usually a good thing. Time will tell whether she's a keeper, so just go slow.
Women are almost always the first to say "I love you (Sounds like "puppy love." to me) It may grow, it may not. Only time will tell. Real love takes awhile. It grows. Yes, sometimes "love at first sight" happens but even that needs to grow. Good luck