I think it sounds like a bad idea. What if, God forbid, through no fault of your own, something were to happen--- horse got sick, burglar got into her house, pipe burst, etc. it could cause a huge rift and negatively impact your therapy. While these are "worst case" scenarios, something more minor could happen too-- she could think the horse looked "unhappy" when she got back, you could put the saddle in the wrong spot, or she could think her house looked "messy"-- or, if you cleaned up after yourself too well, she could think you thought she was messy and were tidying up because she didn't keep her house clean enough. I just think you could be opening up a huge can of worms with this whole situation.

I really do understand the desire to help out and say "yes" to your therapist. Still, I think it's a bad idea.

A few years ago, during a summer when I was not teaching and wanted to make a little extra money, I decided to apply for summer babysitting jobs. My T had lost her usual babysitter and was looking for a new one. She knows I'm great with kids, and said she thought her kids would love me. So there was a temptation for us both to say I should sit for her kids that summer-- but we both knew it was a bad idea and did not do it. There was too much risk of something going wrong, or it simply being too awkward to the point where it would Impact therapy. I just don't think its worth risking therapy over something like a babysitting gig or horse sitting. Therapy is just so important, especially when you find the "right" T! It's not easy to find a new T if something goes wrong.