Is their relationship in trouble?

So, a friend of mine (who I happen to be in love with, and they know it) recently sent me a very sensual love poem written for an ex (though they're not actually planning to show the ex, they wanted to share with someone). The thing is, my friend is in a new relationship now, and doesn't want their new lover to know about the poem or the fact that they're still thinking about their ex. They've been talking about the ex (though it's over 14 months now since they broke up) a lot recently since this new relationship started. What does this mean? Is it just comparing the two relationships? Or does it mean the relationship is headed for trouble or that they still aren't over the ex? Thanks.

Why are you constantly referring to him/her as 'they'?