Dissed! Why Kate Middleton Refused to Curtsy to Queen Camilla at Coronation

Kate Middleton and Queen Camilla aren't letting go of their grudge.

The pair's tension was most recently on display at the May 6 coronation, where onlookers noticed the mother-of-three shockingly didn't do a traditional curtsy when Camilla passed her at Westminster Abbey.

"That obvious insult raised eyebrows big-time," an insider spilled to Radar. "Apparently, Kate was seething over commands Camilla made about coronation guests and decided to make her angry feelings very obvious."

According to the source, the Princess of Wales was particularly peeved that she was only allowed to invite four family members to the historic event while Camilla had 20 guests of her own.

Adding insult to injury, the new queen invited longtime friend Rose Hanbury, the woman Prince William was accused of having an affair with.

"William's affair was vehemently denied, but damage was done and his marriage to Kate suffered," noted the insider. "By inviting Rose, Camilla was going for the jugular!"

The outlet noted that Camilla has been "consumed with jealousy" since the day Kate joined the royal family, which is why she's "relentlessly attacked" the brunette beauty over the years.

And though Kate may "project an easygoing public image, handling difficult situations and people without a misstep ... behind her dazzling smile, she's no pushover, especially when it comes to royal politics," said the source.

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Their animosity will likely become more obvious in the coming months, as the insider explained Kate hid her true feelings about her stepmother-in-law until Queen Elizabeth II died last year.

Camilla has caused quite a stir given she and King Charles' affair led to his divorce from Princess Diana, and in Prince Harry's memoir, he admitted he and William "urged" their dad not to marry her.

The Duke of Sussex made a few other rude remarks about Camilla, including accusations that she planted negative stories about his family and William's in the press.

After the book's release, Fiona Petty-Fitzmaurice, Marchioness of Lansdowne, told a publication that Harry's words did "bother" and "hurt" his stepmother, but "she doesn’t let it get to her."