That's EXACTLY what they told me when my horse was stolen. It's a civil matter, we won't do anything. Good luck.
I got him back, no thanks to those...Ahem.
Just a point here, there's a lot of bashing about the police not getting involved in what amounts to a civil matter. I expect to get flamed here, but there is a good reason for that-they can't, it's forbidden by statute. Bottom line is they have no authority to interfere and would be in violation of the law if they were to do so. Not just criminal law, the police can (and have been) sued in civil court for big dollar damages when they overstep those strict boundaries.
LE deals with violations of criminal law
and their powers are strictly delineated by statute, and they haven't much latitude. Civil law
is another matter entirely, and when a situation falls under that category the law clearly states the Courts are the arbiters in those disputes.
Now the OP's situation is a bit different than the average who owns horse dispute, these people are treading very close to extortion by threatening her. That might be something the local Prosecuting Attorney (they are the ones who decide what can be brought to a criminal trial-not the police BTW) might bring to a trial But, since she hasn't any type of written contract to back up her claim these people were only leasing the horse it walks that razor edge leaning into a civil law "he said she said"situation.
I do hope the OP gets her horse back.