She could be found to be responsible for the care while the horses are on her land. She needs to send a registered letter, giving eviction and starting a lien for feed. She should at least get some inexpensive hay to toss to them , something is better than nothing.
Always do written contracts , and be specific. Good luck. I would contact a rescue, the humane society, animal control etc. I would even go to the mans home, does she know where he works ? I would show up there.