Cecilia S. Lowndes (Cecilia Selby Lowndes), 1889. I’m not sure what date my edition is.
I don’t know anything about the author and can’t find anything on the internet, except that the BL catalogue has 26 books by her, the earliest 1884 and the latest 1894 (so 26 books in ten years). Enid’s Victory (1883) is online as an etext.
Here’s the frontispiece:
And the other pictures.
I’m not sure what the u-shaped thing is – some sort of musical instrument?
Dora, who appears in all of these pictures except the penultimate one, looks older than 15, which is the oldest she can be. In particular, in the second picture she doesn’t seem appropriately dressed for “running” and “replacing [stepping] stones … pulling and digging away at one particularly inviting stone”.