"She is very outgoing and chatty and was basically giggling about it all.
"But after that break Meghan became very secretive and shut down any mention of Harry. It had suddenly got serious."
After the getaway, the pair apparently didn't see each other until September when Harry introduced her to Prince Charles during a shooting party at the Balmoral estate to celebrate his 32nd birthday.
She has met Harry's cousin Princess Eugenie and her boyfriend Jack Brooksbank, and is said to be liked by Harry's friends.
From October 27 until Tuesday this week, the couple were reportedly together at Miss Markle's Toronto home as news of their relationship spread around the world.
The actress has posted a series of romantic images on Instagram since it emerged she had been dating Harry.
She posted a romantic picture of two bananas 'spooning' after news of their relationship broke.
But in her first published interview since then she told the Toronto Sun: "My cup runneth over and I'm the luckiest girl in the world".
A "besotted" Harry, 32, met the actress at a charity event and sent her messages until she said she would meet up with him - and, following a number of dates, the pair are now said to be 'serious' about one another.
They are reported to have spent several days together in Toronto, including a Halloween night at the private members' club Soho House.
Markle, who is from Los Angeles, has been living in Canada for several years while shooting TV show Suits.
But it has emerged that Meghan may have still been with her ex-boyfriend of two years, Canadian chef Cory Vitiello, when she first met Harry and he began pursuing her.
A friend said: "They are the real deal. He definitely pursued her and besieged her with texts until she agreed to a date.
"He is very full-on but she was going through quite a tough time with her previous boyfriend and she was very flattered.
"He's head over heels and she feels the same."
The 35-year-old actress, who is best known for her role as Rachel Zane in US legal drama Suits, is believed to have charmed the royal when he visited Toronto in May.