I wouldn't be concerned unless the woman was an authority on the subject.
A year ago, the ABC show Catalyst tested popular "shark" thinking like dogs, urine and blood attracting sharks; and finding out if dolphins make it safe.
The reporter jumped in with the tiger and bull sharks at Seaworld. Her urine repulsed the sharks. The sharks got interested in the fresh human blood, trying to find the source of bleeding, but lost interest when the blood dissipated.
For dogs, "Apparently, it’s not the smell, it’s the splashing movement and bite sized nature of dogs that’s most likely to attract sharks." and "since 2001, furry animals were involved in 1 in 25 shark attacks on people – that’s way over the odds."
Maybe Jaws would find your pony "bite sized".
As for the dolphins protecting humans, in their test, the dolphin took off as soon as he saw the shark!
"that’s not to say dolphins don’t sometimes rescue people, it’s just that they are not a reliable indicator of the presence or absence of sharks."
Their summary, "So urine won’t attract sharks, a bit of blood might, but only if the shark is within 100 meters. Dogs do increase the risk of shark attack – slightly. And dolphins don’t keep sharks away."
So, pee away, and don't take a Falabella :)
Catalyst transcript for the shark story: Catalyst: Shark Attacks - ABC TV Science

