Meghan Markle's Evolving Fashion Will Give Nod to Princess Diana (Exclusive)

Meghan Markle and Princess Diana
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The bride-to-be will honor Prince Harry's late mother with her style.

Meghan Markle isn't a member of the royal family yet, but she's already reinventing princess fashion.

While the 36-year-old Suits star has been bringing her personal style to all her official royal engagements -- messy buns and trousers -- expect her evolving fashion to pay tribute to the late Princess Diana.

"Like Kate, expect Meghan to make the occasional nod to her husband’s fashion icon mother,” a source tells ET. "Both Kate and Meghan will no doubt honor Princess Diana with designs that reflect her likes and style."

Meghan's engagement ring already features diamonds from Princess Diana's personal collection, but the bride-to-be gave a subtle nod to Prince Harry's late mother at a Commonwealth Day service when she arrived wearing a chic beret by Stephen Jones. The designer was a favorite of Princess Diana and was prone to completing her looks with the same style of hat.

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Meghan is also getting advice from Kate Middleton, who according to the source “has also been advising Meghan about royal fashion, what protocol is expected and how she may have to adapt in the future."

"She has provided Meghan with names of some of the favorite U.K. go-to designers on everything from dresses, coats and the all-important British hat,” a source tells ET. While Meghan will need to adapt to longer hemlines and cut back on sleeveless dresses for more conservative attire at royal functions, she has still charted her own path by going bare-legged instead of wearing the nude stockings favored by most members of the royal family.

As for Meghan’s messy bun that everyone keeps talking about, well, there is no rule for royal hairdos. "There is no royal protocol for hairstyle. Kate often styles her hair in casual ponytail at more informal events, and Meghan’s messy bun was an attempt to fit in with the young people she was meeting in a similar casual setting with Prince Harry,” the source explains.

ET recently sat down with royal expert Katie Nicholl, who reflected on how Meghan's style has already changed since she got engaged.

"If you look at the early engagements that Meghan was doing, particularly that first appearance at the Invictus Games, and you compare that with her very polished and poised appearance at the Commonwealth service... You know, [at the Invictus Games], she turned up in ripped jeans and flat pumps with slightly messy hair," Nicholl explained. "And [then she made] that very polished poised performance at the Commonwealth service. It looks very much to me as if there is someone behind the scenes helping her to dress more royally. She certainly seems to be opting for more conservative designers and really stepping up to the plate in terms of royal dressing and presenting herself as a future princess."

In the meantime, while she figures out how to dress appropriately for her new role, Meghan is also preparing her wedding and making sure she adds her own personal touch. Watch the video below to hear what she has planned. 

Be sure to keep up with all of ET's coverage of the royal wedding right here as we count down to May 19.