YABU. The world's major religions have both major historical, cultural and faith based significance (not that they always concur or have much overlap). Crucifixion is a fact. A man called Jesus, who inspired a 'new' religion is a historical fact. You don't have to be Christian to accept that these 2 things did happen.
I would expect a well rounded education to include a discussion on the significance of Easter (how it came about, why some people find it important etc). Knowing about this does.not for a second force people into a belief, does not force a faith upon them. It's a mention (at your DD's age) of something that did happen and which led to the Christian dominance in the western world that exists today. This dominance has shaped our lives, our world, ever since and is so important.
As a disclaimer, i am an athiest. I don't believe in God. But I believe that a knowledge of religion (different from believing and following in a religion) is as worthwhile as knowledge of any other aspect of history.
You can preface it with "some people believe" without denying the validity of their belief. And as an atheist, I'm aware that my non belief is God is just a belief, no more and no less valid as the beliefs in Catholicism or Hinduism etc.
I do detest the atheist idea that somehow they (we) have the automatic right to be dismissive of all other religious beliefs. And that we are somehow superior in our intellect by profession our non beliefs. I suspect you are feeding her hysteria by being vocal about how such things should it be taught in schools. I