"She convinced there was a conspiracy against her and so she basically put herself in self isolation when she moved to Frogmore," the friend told the publication.
A friend also said Markle grappled with leaving her career behind - and it was part of what sparked the royal couple's decision to exit royal life.
"One of the things Meghan struggled with was not earning an income," a friend said. "She has always worked and I think she felt unfulfilled. Having financial freedom was a big part of them wanting to leave."
"I think she felt like an outsider from the start. This wasn't the life she was used to and she wanted out."
The couple is starting their new life together in Los Angeles, and rumours circulated that British singer Adele was helping them with their transition.
A source told the UK's Daily Mirror that Adele lives five minutes from the eight-bedroom villa that Harry and Meghan are renting from actor and director Tyler Perry.
"Adele's just five minutes from Harry and Meghan and they've swapped notes on the area," the source said.
"Adele loves the neighbourhood. She's also recommended her 4-year-old son Angelo's pre-school and discreet places to take Archie where they won't be bombarded by fans.
"Meghan and Harry want to see how they get on in the area first before they commit to buying somewhere."
