Samantha Markle has questioned how her half-sister Meghan, Duchess of Sussex, can say she "doesn't really know" her, and accused her of "treating people like dishrags".
Markle has insisted "the truth was totally ignored and omitted" in Meghan's tell-all interview with Oprah Winfrey this week, and fired back at her half-sibling after she said she "didn't really know" her.
When asked about Markle's "tell-all book", The Diary of Princess Pushy's Sister, Meghan said: "I think it would be very hard to tell all when you don't know me.
"This is a very different situation than my dad, right. When you talk about betrayal, betrayal comes from someone that you have a relationship with.
"I don't feel comfortable talking about people that I really don't know."
But Markle has now told Inside Edition: "I don't know how she can say I don't know her and she was an only child.
"We've got photographs over a lifespan of us together. So how can she not know me?"
Meghan also claimed Markle only changed her name back to Markle when she started seeing Harry.
She said: "She changed her last name back to Markle ... only when I started dating Harry. So I think that says enough.
"I last time I saw her must have been at least 18/ 19 years ago, and before that 10 years before that."
But Markle, who has the same father as Meghan, Thomas Markle, said: "I was a Markle before she was.
"I thought that was kind of weird that she would say I only changed my name back when she met Harry. Markle has always been my name."
She also added: "Depression is not an excuse for treating people like dishrags and disposing of them."