What are some signs that someone has made a fake account on Facebook?

A friend of my daughter’s (we’ll call her Mary) and her boyfriend (Sam)broke up. Mary initiated it because it just wasn’t working out. The biggest problem, really, was Sam’s weight. He’s pushing 400 pounds or more and it severely limits what he can do.
Mary has moved on, but Sam was devastated.
Then posts started coming up on his feed, things like “I can’t stop thinking about you!” and subtly suggestive stuff. They were supposedly from some new girlfriend.
So I went to check her out..FYI, Sam is Hispanic and is really into super hero stuff.
Her profile pic is basically a Latino Barbie Doll with a skin tight shirt on that reads “Superman.” Just no way! It’s smacks of fantasy more than real life.

So what are some signs people may be making up accounts, perhaps in retaliation against someone else on FB?