What would you do?

We'll say hypothetically you are selling a horse. A girl comes and "test rides" and decides she wants to purchase your horse. She comes out several more times to "test ride."

A month goes by, other people are interested and this girl thinks you are going to just hold out for her. So you let her know "Hey I have a couple other people intersted if you want this horse you need to put a deposit on him ASAP." She recoils and states, "I thought you were going to hold him for me and just let me pay on him until December."

Thus far you have been very patient, basically given her free riding lessons everytime she has come out to ride the horse and offered to allow her to board him at your farm until she finds another location for him. She sets times to come out and ride and doesn't show up until hours later and still expects you to stay out in the barn with her so she can ride.

She uses all your tack and equipment, grooming supplies, fly spray, etc and does rent it or share cost on supplements, fly sprays, grooming products, etc. You have gone out of your way to help her purchase her own supplies only to have her stand you up when you have asked the tack shop owner to come in early for you so SHE can look around. and all this while working 2 jobs and going to school full time, plus, running a child mentoring project and pony club.

Then upon requiring the girl to pay board once she finally put the deposit (a month and 1/2 later) on the horse, and you require she pay it on the 1st of each month (she is already a month behind) and upon the horse coming due for it's shots you ask her (again helping her out) if she wants to have her horse's shots scheduled to be done when you have YOUR horses done since vets rarely want to do a farm call for one horse.

She waits and waits to confirm, she then does and the evening the vet is to come out she sends you a text (doesn't even have the decency to call) and asks if YOU will PAY for her horse and she will pay you back. (wtf like you're her friend or somthing?) Upon agreeing to pay for shots (only because the vet has already been scheduled and is HERE to do shots), you require the person pay the last month's and the coming month's board plus the shot fees on the 1st of the month (in 4 days) in response to this she gets angry and wants to know what the problem is and if "YOU ARE BACKING OUT OF THE SALE OF THE HORSE."

In response to tell her no and that in light of how she has handled the situation thus far she needs to have the horse paid for before he leaves the premises. To which she is furious. How would you handle the situation from here?? I am rather befuddled by this "USER" who for some reason thinks I owe her. I sold her a really good horse for less than I should have trying to give her a break.

I've allowed her to keep it at my farm for several months (it only takes a few days to build a run in and put up fence- trust me I know), I teach her to ride every night she rides (I'm an instructor and I can't not give help when asked for it) because she is a fool and knows nothing, I have paid for the horse's feed thus far, waited a month for a deposit, am still waiting for the 1st months board and she now owes a second, paid for the horse's shots, allowed her to use my supplies, tack, etc. AND gone out of my way and put my name on the line requesting a person open their tack shop 2 hours early so we could go while she had off work only for her to show up at 10am which was the tack shop's normal hours anyway AND the person running it was sick AND SHE DIDNT BUY ANYTHING, she didnt even PRETEND to be interested.

So now I am to the point where if she does not pay her board to date, the shots and her next deposit on the horse tonight I am going to rescind and re-advertise the horse. What would you do?? Do you think I am being to impatient or harsh?