Kids Refusing to do Activities

I have been working with a 4 year old with DX Downs Syndrome for about a year and a half and she has been refusing to do activities that she used to do willingly. For example, she used to like standing on top of the horse while we played games and turn around to face sideways and backwards. Now these activities scare her. Maybe she is just taller and the issue is her center of gravity has changed or she is becoming more aware of what is being expected of her.
In any case, today she cooperated and she did both of these activities without crying.We suspect it is because dad now waits until after the session to eat lunch. Maybe all the carbs made her tired or grouchy. Are others finding a similar situation with kids refusing to do activities that theyused to do willingly? Oh- she talks about riding the horse a lot while at home and even does half seat on her rocking horse- so I think she basically likes hippotherapy.
Barbara Smith, M.S., OTR/L
HorseOT.com