If you mean that she crossed border illegaly as a 2 yo (I don't know the context since I only read this article) with her mother (i.e. that her mother carried her across) that doesn't excuse her

What country are you from? You're quick to say you're not from the US, but also quick to assert US Law. She literally is not capable of committing a crime (could not have entered illegally) at 2 years old. Liability would fall on the parents when applicable.

Seems harsh and unfair but if we(/they=americans) all have papers, why shouldn't she?

We essentially get ours at the hospital as we're born. (Social Security number) That is kept track of by our parents until we are legally able to get our own forms of identification.

She didn't commit a crime by doing something specific, she is doing it by not doing something (getting the proper papers).

There was supposed to be infrastructure put in place to make this possible (naturalization for dreamers) but it has not. This is a failure on the governments part. The Dreamer has done everything they can to comply with a system that has made it very difficult to comply with.