A great loss
When Rio passed away, there was no denying that he left a huge void in the family. Erica and Jane were very down and it seemed like they would not be able to move on from this loss. Then, Erica had an idea. She wanted to get a new horse.
Source: Vibrant World
Billy doubted that replacing Rio would be the answer to their situation. After all, Rio was one of a kind. But he hated seeing his wife and his daughter like this. He knew how much Rio meant to Erica and Jane so he was a bit surprised when Erica wanted a replacement.