If you want my theory. Nando never cheated on A. They broke up, Nando saw that M was a Spanish, age-appropriate reporter, asked M to go on a date, where he gave her a matching bracelet because he is a teenager. A saw that Nando moved on faster than a Peregrine falcon can fly and did not want to see that, which makes sense.
the other theory is that M is a cover up for Nando getting together with Mark or Flavio. Mark, because I like to be in denial. Flavio because it's only a matter of time till he kicks the bucket. Flavio wants his number 1 twink, Nando wants the assets.
FINALLY someone comes up with a good theory, obviously all of this is a plot to cover up the fact that Nando and Mark are getting back together, like the half hug in Spa???? They can’t hide it anymore