The 35-year-old Chelsea footballer was full of affection for his Irish love, calling her his "best friend" in an interview with Red Magazine.
"People say opposites attract," said Frank. "But when you live together, you need to be harmonious, and she’s my best friend.
"She's made me content," he added. "That sounds soppy, but I've been very happy since I've been with her. Our personalities are very similar."
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In the interview, Frank also praised his 35-year-old wife-to-be's wit and intelligence.
"I’ve got a lot of respect for what she says," he said. "She's sharp, I bounce my problems off her, and I'd like to think I help her with her stuff, too."
Romford-born Frank split from his former fiancée, Spanish model Elen Rivas, in 2008 after seven years together.
The separation was hard for Frank and Elen, who have two daughters together. The footballer says he's now happy that Christine has formed a good relationship with Luna, nine, and Isla, seven.
"I had a year of being a single dad and it was tough," he told Red. "Even now, we have our moments – when I've come back from work and I've lost, and they've made a mess in their room, you get frustrated.
"It's certainly helped me having Christine and the bond that has grown between her and the girls," he added. "They will now gang up on me. For me, that’s great, because going into a relationship, the step-parent role is hard. To get to the point where I see the girls saying, 'We've got Chris, and we're doing this,' is brilliant."
Frank also spoke about his parenting skills, saying that he wants his daughters to learn the value of money and gives them £5 a week in pocket money.
"Emotionally, I give them loads and as much time as I can; and at Christmas and birthdays, I do my best," he said. "But I don’t want to get carried away, because I don't want a brat of 13 or 14.
"I want them to go out and earn their own money and enjoy it. They get £5 a week pocket money, but they have to make their beds, tidy their rooms and show good manners."