Paget Brewster will appear in fewer episodes this season, while A.J. Cook was controversially dropped from the show completely.
"I hate it," Vangsness told Zap2It. "That's the short answer. I can't even tell you it's bittersweet, though it is that in reality. It's like being a squatter in a house, since [the producers] have control over what they decide to do. The sweet part is that those women will rise like phoenixes."
She continued: "I can say 'no comment' about things, but I don't think there's anything wrong about speaking your truth about something like this. At the end of the day, it's going to work out fantastically for both those girls."
However, Vangsness explained that she is pleased Rachel Nichols has joined the show, saying: "She's fantastic and I'm so glad she's here. I'm still sore in my heart that A.J. isn't here, but so happy that Rachel is - and they're entirely different things. I can have both of those feelings."
Criminal Minds airs on Wednesdays at 9/8c on CBS.