They are second cousins, once removed. Your own daughter is second cousin to your first cousin's daughter. Her daughter is one generation removed from being a second cousin.
Draw a litle diagram, with yourselves, parents, and grandparents on it, each generation on the same level as others of that generation. Probably best to start with GParents and work down. It is clearer in a diagram.
The relationships depend on whether the people you are comparing are on the same level/generation as each other or a generation up or down.
Top level are your grandparents.
Below that their children, who are siblings to each other.
Below that the grandchildren, who are first cousins to each other (unless they are siblings to each other).
Below that those of the same generation are second cousins.
Below that third cousins and so on.
If you have to go up a step from one generation to another, they are cousins once removed. If two steps, twice removed,and so on.