Depends on how smart she is I guess. It is kind of a rare thing for a 5 yo to understand graphs, I think, but maybe she can.

It might mean more to explain some of the cool things you can do with calculus (that a 5 yo would find interesting) rather than how it works.

If she seems interested in math and science stuff there's all kinds of cool things you can do with her.

Explain the difference between coasting on a bike and pedaling. When you pedal, you speed up. Calculus compares how much faster one person speeds up than another.

At 5, she's not going to grasp charts or numbers, but something familiar to her could work.

Source: father of three and taught my oldest basic algebra (variables) so we could make a game on Scratch together when he was 6 or so.

It is about knowing how the change of things affects things mathematically.

My mom was going for a math degree when I was around that age. I was naturally curious about what she was studying. What stuck with me though has been ways of thinking and concepts. It has been a really good thing for me in real life as well as academically.

My suggestion would be to focus on concepts and lean hard on why. The practical 'how' is something that takes lots of time to learn and is incremental (addition then subtraction and so on). The why can be highlighted in movement, natural shapes, thoughts on time/light/infinity, and things like that.

Calculus specifically I would approach by asking how many sides does a ball have. Is it one, zero, or too many to count? The 'right' answer doesn't matter in this context. The important part is to learn that they all kind of mean the same thing if you think about them in different ways. Calculus uses thinking about it as too many to count to answer questions that are hard to answer when you think about it as zero.