C.T. Tamburello and Diem Brown C.T. Tamburello and Diem Brown

What happens when you agree to participate in a reality TV competition, and then find out your ex will be there too — as your one and only teammate for the entire game? Just ask Diem Brown, a veteran of MTV's Real World/Road Rules Challenge shows, and competitor on the network's upcoming The Challenge: Battle of The Exes. The show, which premieres Wednesday, Jan. 25 at 10/9c on MTV, pairs up former flames for a chance to win $300,000. Brown, who was forced to reunite with her ex-boyfriend C.T. Tamburello, calls the experience "insane," and teases, "There's going to be tons of hookups, tons of fighting and unresolved issues." TVGuide.com chatted with Brown about what to expect from this season, why she decided to stick it out, and who proved to be her biggest competition.

At what point did you find out you would be paired with your ex-boyfriend?
Diem Brown:
I didn't know until I showed up. The second that I found out it was "exes" I was like wait a second... this person right next to me, this person that I haven't spoken to in 3 years that I can't stand to look in the eye, I have to pair up with him? I wanted to walk away, 100 percent.

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So how come you decided to stay?
I really wanted to promote my charity, MedGift, which is a gift registry for cancer patients. I said I would give 100 percent of whatever money I got to the patients.

Can you talk about how the charity started?
I got ovarian cancer when I was 23, and as a result of treatment I was down to 93 pounds and I lost all my hair. I felt like a monster. My girlfriends in Georgia that were getting married, they could put their wedding registries up and I could give them a gift right away, but all of my friends who wanted to help me, as a patient, I had no resource. I looked for a company that would let people put money toward a medical bill or a wig and didn't find one. So I decided to create it. In my first year we helped over 100,000 families. We're now in our fifth year.

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That's amazing. Do you think your competition saw you as a bigger target because you went into it with a higher purpose?
Working for this cause totally worked against me! People would be like, "Well, I can't compete with that!" They know me and they know for a fact that I would have walked out in two seconds if it wasn't for this charity.

Once you smoothed things over, did you and C.T. come up with a strategy?
We fought every single challenge. In the beginning, we did not work as a team whatsoever. I thought, "I'm smarter than you, so you should just follow me." And of course, he didn't like hearing that. He knows how to push my buttons and I know how to push his.

Who did you see as your biggest competition?
Ty and Emily. They look like they could be on the cover of a fitness magazine. She eats 2 pounds of meat per sitting!

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It sounds like it should be a pretty dramatic show, to say the least.
There's so much craziness that happens throughout the whole season. No one wants to put themselves back in a situation where you're with an ex. It's not an easy transition. It's going to be insane.

What can we expect to see on the premiere?
Awkward tension. Trying to get closure from an ex, and yet getting stuck in honey 40 feet up in the air and then having to lick it off of each other to win. Ridiculous!

The Challenge: Battle of the Exes premieres on Wednesday, Jan. 25 at 10/9c on MTV.