I hate that question and I never answer it. For one thing, I really truly am terrible at guessing how much people weigh. I just have no idea. So I usually just say that I'm terrible at guessing weights. If they persist, then I just say, a little more seriously: "I'm not going to guess your weight, let's move on to another topic," or "Let's not play this game." If you flat out refuse to do something, most people won't challenge you further on it. I use this approach with a lot of things that people try to pressure me into.
Lily, I think you were right to guess low. If you had guessed high, I doubt it would have changed her perception of herself, it just would have made her made at you.
