No, they are not having an affair, but they did have lunch together on February 9, 2011.
According to the Richard Kay, a reporter from the Daily Mail, Britain’s future Queens dined at a new restaurant at the Berkeley Hotel in Knightsbridge. Catherine wore her hideous trademark black suede books, beige blazer (another trademark… freaking blazers), black tights, a patterned dress, and a globs of black eyeliner (another trademark.) While Camilla wore a purple plaid number that made everyone dizzy when they looked at her outfit. Apparently, Catherine’s sister, Pippa, joined the cuddly lunch along with Camilla’s daughter, Laura.
It is unknown what the group talked about during their time together; however, according to the Daily Mail:
A fellow sitting just two tables away, tells me: ‘All four women were talking away like mad and none of the waiters could get a word in edgeways to serve their lunch.
I heard Camilla saying… ‘if I can give you one bit of advice…’ Kate was really enjoying the moment.
‘I did hear talk of trumpets and someone said ‘we can’t have trumpets, the ceiling is too high’’, which may have been a reference to Westminster Abbey.’
To read the rest of the article and to view several photos please click the link: Daily Mail
royalcorrespondent.com 
I foresee a period of relative peace in the British Royal Family. I’m excited to see it happen. Although some may prefer conflict and drama, it’s so much more interesting (in part, because it’s so much more challenging) to watch a family unit together and enjoy each other. Also, Kate and William are better together than apart. Plus, William and Harry have a nice dynamic. Same with William and his father. Maybe we’ll see their real personalities and real happiness. Glamour and excitement don’t have to stem from pain and immaturity (both of which defined the 80s and 90s for this family).
I completely agree with you, K. 🙂
Thank you for commenting as well!