The 27-year-old former reality TV star - who is reported to be preparing to tie the knot with the 33-year-old rocker turned law student - posted a photograph of them both on Instagram along with a touching message, to celebrate their one-and-a-half year anniversary.
She wrote: ''Just looked at the calendar and realized it was a year and a half ago today that I met this guy...And I sure am glad I did (sic).''
Lauren recently insisted she and William are perfect for each other because they have so much in common.
She said: '''He is very good for me because we have a lot in common as far as where we grew up. It's the first time I'm with someone and I'm not explaining things.
''He also has experience in the entertainment industry, so he understands a lot of things that people don't always get.''
Lauren also said she will never appear on a reality show again because starring on 'The Hills' and 'Laguna Beach: The Real OC' caused people to judge her harshly.
She said: ''It feels done for me. I'm OK with it being done.
''I only ever got to tell half my story. People are very quick to judge these days, especially behind the anonymity of a screen name.
''It's very easy to say, 'I hate her, I hate what she wore, she seems mean.' But you're only seeing a small fraction of her life.
''There is always gonna be a little bit of...negativity, which just comes with the territory. You realise it doesn't matter. It's so simple, but it's a very hard lesson to learn. At the end of the day, it doesn't really affect you in any way.''