I’m afraid I don’t have a lot of details in trying to identify this book, but here’s what I’ve got:

It was a young adult book that came out in the early to mid-‘80s – I want to say no later than 1985.  It was told first person from the view of a teenaged girl with a very strict mother who monitored everything she did.  The girl (I don’t remember her name) didn’t fit in at school and wanted to have clothes like the cool girls – I think the mom insisted on sewing all the girl’s clothes herself.  She secretly went shopping and bought a pink angora sweater and cranberry-colored corduroys and had to hide them from her mom.

I also seem to remember that the cool girls were riders at the local horse stables, and the girl wanted to ride there to be like them, even though she didn’t know how to ride. What sticks out most in my memory is that the writing style was very formal and stilted.  I remember one such sentence: “The following morning, rain was falling when I woke.”  Another was when the mom ultimately discovered the girl wearing the secret outfit and “Mother knelt to examine the construction” of the pants.