Totally Horse Mad
This series is about a girl called Ashley, she loves horses but unfortunately does not own one until she moves to the country and finds an abandoned horse that her parents agree to let her keep so long as she pays for everything. It's all about the adventures of Ashley her horse Honey and her best friend Becky and her horse Charlie.
The first book is called Totally Horse Mad, #2 is Horse Mad Summer, #3 is Horse Mad Academy, #4 is Horse Mad Heroes, #5 is Horse Mad Western and #6 is called Horse Mad Heights.
You've just got to read them they are so good!!!