In recent weeks, fans have seen Glenda enjoy a secret relationship with Phil while also seeing his long-time nemesis Ian Beale.
Speaking on This Morning today, Barber explained why Glenda has found herself entangled with both men.
Asked whether Phil's "alpha male" status is appealing to Glenda, the actress replied: "Exactly - and he's a bad boy. So I think she quite calculatingly decided that he was going to be her man, but she does fall for him along the way.
"And then, of course, he doesn't treat her very well - and the worse he treats her, the more she likes him."
Discussing the benefits of sleeping with Ian, she added: "I think she needs Ian to bolster up her ego, because Phil treats her badly, she loses confidence and then you've got Ian Beale, who's always there, who's always available - he flatters her and he pays her rent!"
Later this week, fans will see a mystery assailant attack Glenda after she becomes rude and insulting at Ben's welcome home party.
> Click here to read our EastEnders spoilers