The photo was cut from a larger one using scissors and then pasted onto a gray sheet of card stock. It is quite small — only 3" x 3.5" — and has deteriorated with age. Enlarging the part that shows Clara reveals few additional details.
Someone wrote on the back of the photo that the dog was named Perry. Clara loved dogs all her life, evidently including this one. Photos with animals were still quite unusual at this time since even in bright light conditions the exposure times had to be a quarter of a second or more and animals could not be counted on to hold still for that long. The photographer evidently relied on a third person to attract Perry's attention in hopes he would poise alertly, as evidently he did, long enough for the exposure.
The photo doesn't show much of the grounds of the Windmuller estate. You can see that Clara stands in a garden surrounded by trees and other plants.
Both "Hillside" and "Woodside" are descriptive names. The Windmuller estate was located on a wooded hill in an area where marshy lowlands alternated with wooded uplands. Woodside was part of Newtown and "Newtown" is not in the normal sense descriptive, having been "new" in 1665 when the Dutch still ruled in New Amsterdam. I've written about Woodside before; see in particular Woodside, Newtown families, and Bragaws.
 Wikipedia' article on fashions of the 1890s says that dresses like Clara's began to appear in 1892. They had low waists and high necklines and their sleeves had a high, gathered head and were fitted to the lower arm.
These two images show daytime dresses that young misses might wear in the summer.
Of the one on the right, a web site called Victorian 1890s Misses' Summer Dress says: "This young misses' dress dates to the late 1890s and features a fitted bodice with ruching at the neckline and fitted, ruched sleeves with a ruffled cap at the shoulders." (Ruching is another name for gathering or bunching. It was used to make ruffles and flower petals as well as simple gathers.)
Here's an example of a more elaborate garden dress.
 Compare this formal portrait of Clara which was taken at about the same time as the photo of Clara with Perry. I took the one to its right in 1954 when she was 84 years old. In the latter you can see she's holding a leash. She doted on dogs then as, apparently, she did when young.
 HISTORY OF QUEENS COUNTY, with illustrations, Portraits & Sketches of Prominent Families and Individuals (New York: W.W. Munsell & Co.; 1882)