"It's still weird to her that no one hugs and that everyone is so uptight, especially Kate. She said it's obvious that Kate and William do not approve of their choices and that you could cut the tension with a knife. Kate barely even looked at her and their interaction was kept to a bare minimum," the friend added.
The Duke and Duchess of Sussex had a tense and brief exchange with the Cambridges at Westminster Abbey on Monday.
The Sussexes walked in ahead of William and Kate, before Prince Charles and Camilla arrived and the Queen then made an entrance to trumpet fanfare.
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There was an awkward "hello" to William and Kate but not much more. It was the first time the two couples saw each other since "Megxit" news broke.
Meghan reportedly told her friends she was "relieved" she didn't take Archie to the UK but has been FaceTiming him during the trip.
"She said it's not like she was intentionally keeping [Archie] away, but it made no sense to bring him and put him in harm's way," the friend added.
Markle is said to be worried about coronavirus and wanted to avoid unnecessary travel for Archie.
Harry is expected to fly back to England for the London Marathon on April 26, as he is a patron of the event.