"Given our concerns for the welfare of the animal and the distress that it appears to be under, I will be forwarding it to an SPCA inspector who will complete an investigation."
She said it was a "stupid and thoughtless act which the SPCA Auckland disapprove of very strongly indeed".
"This is clearly an animal in distress. It's a horse that's in the wrong situation; it's in the city, it's at night, there are intoxicated people around and it's very noisy."
A police spokesman said the woman thought "it would be fun" for the patrons to have a gallop around.
She was charged with being drunk in a public place and disorderly behaviour while the horse was picked up by an animal control officer. It has since been returned to the woman.
Revington's Hotel owner Therese Gibbens was annoyed that the woman's actions reflected badly on her hotel and on Greymouth.
"It doesn't reflect well on, not just the hotel, but that whole misconception about the `Wild West', which is just rubbish anyway.
"We don't want to be tarred with those sorts of brushes. [Greymouth is] just another New Zealand town, where someone was silly."
The woman had come to the hotel today and apologised.
Police said there had been no complaints made against the officers involved in the arrest.