Not dismissing her health problems, but at this point in a campaign, the Presidential candidate's Secret Service protection is akin to the President's protection, scaled down just a bit, but does include an ambulance and even a counter-assault team. I would bet that if you went looking for it, you would find one in Trump's protection team too.
updated, here is a picture of Trump's motorcade arriving at the GOP Convention and you can see an ambulance about 5 vehicles back.