The former tabloid reporter has claimed that she quit her job with Star magazine after falling for Gosselin and was devastated when he dumped her for 22-year-old Hailey Glassman.
Speaking on CBS's The Early Show, she said: "I don't have a lot of respect for him. I think he handled the situation very poorly. He did not act like an adult or a grown man or a father. And it's just sad.
"I think the fame has gone to his head and he's on some bachelor romp or whatever you want to call it. You cannot treat people [like that]. It's not fair to me, it's not fair to Hailey, it's not fair to his ex-wife, his kids or anyone else involved in the situation."
Responding to footage of Glassman describing her as "cuckoo", she said: "I feel badly for [her] that she doesn't know the truth... Any guy that cheats says that the other woman is cuckoo or crazy... I have nothing bad to say about her. This isn't about Hailey and I, this is about Jon and I."
Major added that she is no longer in love with Gosselin and is still hoping to continue her career as a journalist.