The Queen was understood to have taken Letizia under her wing and helped her learn the royal ropes before her marriage to Felipe.
WATCH: Queen Letizia appears to confront Queen Sofia after 2018 Easter Mass
Pelea en la Casa Real porque Letizia no deja que Sofía se haga una foto con sus nietas. pic.twitter.com/LEjCk2nm0A
— El Rabillo del OjO👁️ (@rabillodelojo) April 3, 2018
The two ladies had become so close that Letizia even paid tribute to her future mother-in-law during her first speech since becoming engaged.
"From now on, and more and more, I am going to integrate fully in this new life with the responsibilities that come with it and with the support and affection of…" Letizia said.
Letizia and Felipe's engagement was announced in November 2003
"… With the affection of the king and queen and the priceless example of the queen."
There have been reports of tension between the two royals over the years
Following speculation in the press, the two ladies appeared to publicly clash in 2018 when the family attended Easter Mass at the Cathedral of Palma de Mallorca.
The outing had intended to be a show of unity; Felipe asked his father Juan Carlos to attend – he had been absent from the event since 2013. His surprise abdication would come the following year.
However, all eyes were on Sofia and her daughter-in-law as the family left the cathedral.
The family photographed after Easter Mass in 2018 - moments after the public clash
Sofia, a doting grandmother, seemed to be preparing to have her photo taken with Leonor and Sofia when Letizia seemingly moved to block the shot.
So stood directly between the trio and the cameras and was seen removing Sofia's hand from Infanta Sofia’s shoulder. The two ladies then exchanged words before Felipe stepped in.
Letizia pictured with her mother, Paloma
The exact reason for their tense interaction is not known. It has been speculated that Sofia felt increasingly cut out of her granddaughter’s lives; Letizia's mother Paloma Rocasolano became a regular presence in the palace and was known to take care of the girls when their parents travelled.
Happily, in recent years, stylish Letizia and Sofia seem to have put aside their differences.
Letizia and Sofia in August 2022 with Letizia's daughters
In August, they happily posed for photos together during the family's annual summer holiday in Palma de Mallorca, with Sofia smiling as she sweetly linked arms with daughter-in-law Letizia.
And then in January, Letizia was on hand to support Sofia at the funeral of her brother, King Constantine. It was during this visit to Athens that Queen Letizia also reunited with Crown Princess Marie-Chantal; the pair were thought to have fallen out over the Easter Mass video.
LISTEN: KING CHARLES: THE MAN BEHIND THE CROWN
Make sure you never miss a ROYAL story! Sign up to The Royal Explainer newsletter to receive your weekly dose of royal features and other exclusive content straight to your inbox.