Samantha's partner Mark has been quoted as saying he took her to hospital and she seems to have suffered a broken ankle and fractured knee in the incident. The boyfriend swung the auto to the side to avoid hitting the other vehicle but crashed into a concrete barrier instead.
While Samantha insists that she's not talking ill about Meghan, only defending herself, she states: "This is not Great Britain".
The alleged incident came after Samantha gave interviews on United Kingdom television about her half-sister's upcoming wedding to Prince Harry.
Samantha struck the windshield during the crash and was shot onto the floor. "If it's about my life or my father's, there's something in this country called freedom of speech".
Ms. Grant told TMZ she does not have a relationship with Meghan Markle, with whom she shares a father.More news: White House adviser: U.S. wants China trade deal as talks resume
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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. "I'm not taking it personally, nor am I holding it against her".
Days before the royal wedding takes place in England this weekend, Meghan Markle's family continues to serve up major drama stateside.
Thomas had stents implanted in his blood vessels, and will remain in hospital for "a few more days" but he will take "a long time to heal".
"She doesn't have a copyright on that and she's not going to tell me that I can't speak about my own life or my father's where it's a matter of public self-defense because the media is disparaging us".
Meghan and Harry will marry at noon on Saturday at St. George's Chapel at Windsor Castle.