Horse & Pony Books:
MY LIFE WITH PENNY
aka LIVET MED PENNY (Original title)
(STABENFELDT/PONY [NORWAY?/USA] 2009?)
SUMMARY: When on a trip to Spain, Julia is sure she will be missing her pony Penny too much to enjoy it. But as she begins to ride the big Spanish horses there, she begins to wonder if she may need a new bigger pony. Sure enough when she returns home she finds she has grown 3 inches and now Penny is too small for her! But how can she give up her best friend to make way for a bigger model? It isn't until one of the horses at the stable is abused by its owner that she starts to formulate a planů.
I think this was published by Stabenfeldt in both its Norwegian and American divisions. It is fairly easy to find in the USA, (and presumably Norway) but a lot harder elsewhere.