Bella was not aware that Ben Crouch had told anyone of their adventure in the Irish pub, especially a gentleman Bella couldn't identify by voice or sight. It would have been less alarming — well, not alarming at all because she wouldn't know — if he'd told someone who planned on keeping it to himself, but this gentleman was confronting her!
She opened her mouth to deny it, but she couldn't figure out the words to combat his argument. She still wasn't really sure if Ben was the source of his knowledge, but judging on his words, she concluded that it likely was. He'd never seemed like the most responsible man in the world, but she didn't expect him to be such a blabbering one! Even she hadn't revealed the events of that night with anyone, and she was the biggest loud-mouth in magical Britain!
"Why are you telling me this?" she asked suspiciously, wondering if he had a purpose for this confrontation or if he was simply there to make her feel bad about herself.
She opened her mouth to deny it, but she couldn't figure out the words to combat his argument. She still wasn't really sure if Ben was the source of his knowledge, but judging on his words, she concluded that it likely was. He'd never seemed like the most responsible man in the world, but she didn't expect him to be such a blabbering one! Even she hadn't revealed the events of that night with anyone, and she was the biggest loud-mouth in magical Britain!
"Why are you telling me this?" she asked suspiciously, wondering if he had a purpose for this confrontation or if he was simply there to make her feel bad about herself.

— MJ is MAGICAL —