The Fantasy: My 21 Yr Old GirlFriend

We have been boyfriend and girlfriend for a few years. We are both very loyal and loving to each other. A few weekes ago, while on a date, we did not do anything sexual, mostly we do BJs for me and dry humping for her to get us off. (she doesn't like the idea of having sex in a car like teenages) So one time I was on my computer, looking at porn, I came upon the concept of cuckolding. It wasn't long before I wanted porn of it and fantasized about trying it. She would probably say that I was a sick pervert. I have brought it up when I was takes, so its always been kind of jokingly. And she never gave a response. I have always wanted to tell her my fantasy but I really have no clue how she would react. I want to share my fantasy with her. I have offered to buy her a dildo but she wasn't really sure about a dildo sense she rarely masterbates.
Firstly, I love interracial porn, I do not know why. I would love her to pick out a Black man with an 8 inch or 9 inch penis, since mine is only 7 inches. I would love to be in on the threesome and if not get to watch, take pics or video tape. She is peticulaer and doesn't like cum on her face nor in her without a condom. Mostly, I would just like to get to see her fucked well by a well endowed black man. I have made her orgasism during sex but I think htat a well hung black man could do better. I think she deserves to see who to get fucked well before we get married. (we want to get married after school and I have been the only man that she has had sex with. So she only knows how we make love and I think that a black man with a bigger dick could give her better sex. Her white face and beautiful lips sucking on a black cock. Then his long black penis working its way through her tight vagina, making her feel in ways that I never could. I am sure that they would fuck like bunnies all day. The ideal place for him to place his load is on her face, but she's kind of picky about that so she would probably swallow his load. This would be my fantasy. Mybe I will show her this post, I dont know.
Does anybody have advise?