The socialite - who is 11 weeks pregnant with his first child - poured her heart out in an emotional post on Instagram shortly after she had returned from a New Year break with both her husband and the 53-year-old music mogul.
She wrote: ''Throughout life you will meet one person who is unlike any other. You could talk to this person for hours and never get bored, you could tell them things and they won't judge you. This person is your soulmate, your best friend. Don't ever let them go.''
According to E!, the message is said to have been posted on her account - which she closed six months ago - around the time ''things developed'' between the pair.
Lauren also added a comment to her own message, writing: ''True friendship and true love are rare like diamonds. To be cherished and treasured and to be held onto with all you've got. Be kind.
''Love with raw passion and with all your heart. And finally, strive to learn and practice the act of forgiveness. X (sic)''
Reports have claimed her ''forgiveness'' comment could be a reference to her now estranged husband, Andrew Silverman, with whom she has a seven-year-old son, Adam.
While Andrew is believed to have been outraged upon finding out 36-year-old Lauren is expecting Simon's child, friends recently suggested the entrepreneur was aware of ''warning signs'' earlier in the scandalous fling, which may have began as early as 2009.
Andrew filed for divorce from Lauren three weeks ago, citing the 'X Factor' boss as a co-respondent in papers and blaming adultery as the reason for the failure of his marriage.
Simon is said to have offered the brunette beauty her own plush property on the Trousdale estate in Beverly Hills, California, when her marriage has been legally dissolved.
Since returning to his musical ventures in 2013, the former Reuben vocalist has become a valuable member of the British alt-rock scene.
Listen to Little Suspicions' debut single 'Wasting All My Time'.
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