Whether it is the Tooth Fairy, Santa Claus, the Easter Bunny or the Great Pumpkin - why do we as parents "lie" to our children when we know that in a few years they will learn the truth and possibly have hurt feeling?
I know / understand that it is all in good fun (at the time) but I also know my younger daughter was very hurt when she learned the truth. She told me that she would never believe anything I told her again when she found out the "truth."
After that, If I could do it over, I do not think I would have "lied."
I remember being quite hurt as a child and learning that my parents knew something wasn't true, and that they had told me it was. I think it can harm the trust relationship, so I chose not to tell my kids those lies. I did tell them about those pretend characters -- I'm all for fiction and fun and imagination -- and watched Rudolph, Frosty, etc., and my kids are all grown now and are not at all unhappy that they never "believed in" Santa, the Tooth Fairy, the Easter Bunny, etc. They also know that I am honest with them, and that if I tell them something is real, it's because I believe that it is (such as God -- for me, Christmas is about Jesus, so we always made a birthday cake instead of leaving cookies out for Santa, and we sang "happy birthday" to Jesus.)
Through the years I have met many parents (I think most, really) who tell their kids at least about Santa -- some even writing "from Santa" on presents. I think that they do it because it feels like magic for a child, and they like seeing the delight in their children's faces. For me, though, the key for most kids believing these things is the fact that their parents tell them it's true. If it was coming from someone else, they wouldn't believe it as readily as they do when Mom and Dad are saying it.
Some parents don't think of it as a "lie" either -- but it is. If you ask most children, they will tell you that a lie is saying something you know isn't true as if it was. I guess some call it a "little white lie" because it doesn't hurt anyone -- or it's not intended to hurt anyone (although, as I think most of us know, it certainly does hurt some kids).
We live in a society that condones telling children these things as if they are true, and I think it's up to each parent to decide what to do. But I do think that parents should sit down and discuss it before having kids, or when the oldest child is very small, and decide then if they want to do it. I think most people do it because that's what their parents did, or it's traditional, or something like that. For my DH and I, it came down to, "Do we want our kids to trust us and believe us when we say things, or not?" Just because something has been done for years doesn't mean it's the right thing for our particular family, so we opted to always tell our children what we truly believe is the truth.
I'm sure that your daughter will in the long run trust you again. I do think if it were me, I'd apologize and let her know that your heart was in the right place, but that you're human and made a mistake, and that, just as I'm sure she's made mistakes, you will try to earn her trust again. And then do what you can to make her see that you really always did have her best interests at heart, and that you are there for her.
-LadyZ