Hoffman and David T. Hargitt, 22, also of Grandville, were stopped by Huron County Sheriff's Deputy Shannon Lyons on Greenwich Milan Townline Road.
"They were down here in Ohio partying at a campground and then on their way to Cedar Point," Detective Sgt. Josh Querin said shortly after the arrests were made.
Lyons stopped the vehicle, driven by Hargitt, for speeding. Deputy John Vogel then assisted at the scene with a K-9 unit.
Hargitt was found to be in possession of marijuana. He said he had a medical clearance card for the marijuana from Michigan, said Querin, who added that doesn't permit Hargitt to have the marijuana in Ohio.
Hoffman, a passenger, was found to be in possession of numerous suspected Adderall pills for which authorities said she didn't have a prescription.
"Brownies, containing hashish, were also found in the vehicle," Querin said.
Hargitt was charged with speeding and also issued a summons on possession of marijuana.