Samantha Markle, the outspoken half-sister of Meghan, was reportedly turned away from the Duchess's doorstep after arriving uninvited.
Samantha, 53, flew into the UK with the aim of confronting her half-sister but pictures appear to show her being met with a wall of silence after an embarrassing stand-off with palace security.
The move culminated in Samantha, who suffers from MS, handing over a note to Kensington Palace security before buying Royal merchandise, with Daily Mail acquiring photos of the encounter.
Bizarre pictures show Samantha clutching a Harry mask that she bought from a souvenir shop after refusing to leave the Royal area.
Samantha flew in two weeks after palace officials received a letter saying her behaviour would "escalate" if they did not arrange a meeting with the Duchess, according to The Mirror.
It is the latest in a string of high profile public bust-ups with the palace after an on-going family feud involving her half-sister and father, Thomas.
A source told The Mirror that the fact Meghan's older sibling was turned away "speaks volumes".
The source said: "The ongoing feud between Meghan, her sister and her father has so far been played out in public interviews and communication across the Atlantic via aides and representatives.
"This was a huge move on the part of Meghan's sister to try to see her face to face and the fact she was turned away speaks volumes.
"This is the closest Meghan has come physically to that side of her family since she married into the royal family but palace staff had clearly been instructed not to allow her access."
Samantha, being pushed in a wheelchair by her partner, got closer than ever to Harry and Meghan since their lavish marriage in May but the move is likely to cause further ire from the royal side.
The timeline of Markle embarrassment moves in peaks and troughs, with the silence likely worrying the palace in regards to what the next Markle move will be.
In May Thomas Markle sparked a whirlwind of media attention after being exposed for selling pictures to paparazzi before the royal wedding and then giving a tell-all interview to British TV.
In the interview with Good Morning Britain, the 74-year-old leaked details of private conversations with Meghan and Harry before telling US press he felt 'frozen out'.
Samantha lashed out at the couple afterwards, calling her 37-year-old half-sister 'cold' for ignoring their dad before dubbing her "DuchASS" and her husband Harry a "wuss".
Samantha first hit out at her famous half-sister after her romance with Prince Harry was revealed, branding her a "social climber" who is "not fit to be a royal".
She then announced that she would release her memoirs and that her sister should prepare herself for some home truths.
The public spat was accentuated after Samantha did not receive an invite to the royal couple's May wedding.