Great advise by all. When I write an ad I do it first in Word then I can look at it a while, tweak it, and finally use spell checker.
As for the last sentence ... I'd eliminate it altogether. My question when looking at the ad would be "If she is going to miss her, why is she selling her" and "Why does she have to go". There are also too many negatives in your ad.
Just my $.02 from buying and selling a lot of horses.