It is a Scam! I totally agree with LB, there is no way that a horse trailer would be shipped by air on a military flight to NB.
Now how are you going to tell her? "this ad is a scam and will not happen" I think that is the best way to tell her. If she does not believe you, then she deserves to lose a couple of thousand dollars. Don't worry about hurting her feelings, cause sometimes the truth hurts!
Stay away from anything that seems too good to be true. If you do find something (horse trailer, motorcycle , puppy) that seems like a good price and then the seller tells you that all you have to do is send money (mostly by Western Union) and that it will be sent by air plane, it most likely NOT going to happen. I work in the airline cargo business, and you would be surprised how often I get calls about expecting a dog from such and such place and that it is suppose to arrive by plane and be delivered to their house. Oh and that they had already paid for the item. Say good bye to your money honey!
Good luck and keep clear of these scams!