I would just walk away. She's owed you for over a year, so it's not making the difference between whether your horse eats or not and carrying around the anger at her is doing more damage than good. Even if you get the judgement, chances of collecting are very slim. Not to mention, she owes you $1200, you have to file, another $150-200, and because she's out of state you'll have to pay someone in her state to serve her, another $50 or more, then a day in court so lost wages, gas money and probably eating out at a restaurant. You're also looking at various postal fees to send all the certified, return receipt letters you'll need to send to show how you've done your due diligence on collecting the debt.
Sounds like throwing good money after bad to me.
I'm not just talking to hear myself speak either. I went and got 3 mares from a client in KS, brought them down to my ranch for breeding, fed them back up to a healthy weight, bred them and sent them home in foal. I ended up getting stiffed for over $2500. I wrote it off as a loss. No point in wasting time & money when my chances of actually getting paid are slim to no good.