Listen though if you consider that nelly is fake it explains a lot of Niall’s behavior during promo season. The boys kept bringing up Niall stealing girls/being a lady killer, probably instructed to do so by management. Niall was pissed because he wasn’t super on board with getting a PR girlfriend and acted irritated because of it.
I know that some people feel like he was mad because the boys were poking fun at his relationship - but I always got the feeling that they wouldn’t purposely bring up something he was so annoyed about unless management was telling them to. Like, that seems like a really dick move to continuously mock your bandmate for stealing girls and then have his girlfriend become public and have it be super easy to trace that her breakup with her last boyfriend was messy and he implied she cheated. That doesn’t seem like something the boys’ would make light of in interviews.