Mustang Mountain Wild Horse by Sharon Siamon

Step into the wild up on Mustang Mountain.
 
'I don't want another horse.' Alison tossed back her haor. 'If I can't have Duchess, I'm never riding agin.'
 
Becky and Meg are thrilled by the promise of riding wild horses, but Alison can't stop thinking about her father selling her own horse, Dutchess. Just as her holiday seems to be falling apart, Alison discovers a wild mare in need. With the help og good looking Josh, Alsion comes up with a plan to save the sick horse.
 
But can she save the mare beforeit's too late?