A Cowgirl appeared in The Secret Life of Toys episode "Happy Hortense to You." A new toy, she arrives during Penny's birthday party. She's a cow and a girl, so that makes her a cowgirl. The rambunctious cowgirl repeatedly tries to lasso Hortense, who insists she's not that kind of a horse. In the end, however, her rope skills prove useful in extracting the other toys from a fallen table.
The cowgirl appeared as a background character in other episodes. In "I'm Going to Tell...," she is part of the toy orchestra, playing violin (or in her case, most likely fiddle).