The 53-year-old is believed to have broken her ankle in the crash, which is reported to have involved a photographer in the other auto.
Her boyfriend tells TMZ that they had a "paparazzi confrontation" near a Florida toll booth.
Grant's boyfriend Mark (last name unknown) told the gossip website that they were traveling in a vehicle near a toll when another auto swerved in front of them.
Uh oh! Another member of Meghan Markle's family has ended up hospitalized in the days ahead of her royal wedding. The boyfriend claims he drove Samantha to the E.R. where she's being checked out for a possible broken ankle and fractured knee.
After Meghan wore a £56,000 designer dress for her engagement photo, Samantha said: "If you can spend $75,000 on a dress, you can spend $75,000 on your dad".
Samantha is now being treated in hospital.
In addition, she admits that the princess-to-be doesn't even have a relationship with anyone else in the family, at least to her knowledge. "If it's about my life or my father's, there's something in this country called freedom of speech. Staying in the hospital a few more days", he told TMZ after the procedure on Wednesday.
The images - which appeared to show a lonely Mr Markle browsing images of his daughter and Prince Harry in an internet cafe, lifting weights to get in shape for the wedding, and being fitted for a suit for the big day - have allegedly netted up to $180,000.
Samantha didn't receive an invite to Prince Harry and Markle's royal wedding. As she has MS, she was not able to lift herself up.
She added that she would like to give the present to Markle personally.
Samantha and Meghan's father Thomas announced on Monday night he wouldn't be attending the wedding, after he was accused of working with a photography agency on staged paparazzi shots.
"I'm ok. It will take a long time to heal".