My gf and black cock fantasy!

So a while back I posted on here about my gf and how I have this fantasy of her taking black cock. I seen an interracial porn scene and that’s what set it all off! Every time I fucked her that’s all I thought about…everytime I jerked off it was an Asian girl being fucked by a black guy. She was never been into coloured guys, not for a racial matter I just think it was a preference. We do role play on occasion and talk dirty while fucking. One time I brought up something about her being a little slut and taking black cock all day. She wasn’t into it…and was like uhhhh….it was akward. Kind of shut me down abit, felt embarrassed. Here’s where I’m going with this guys….don’t give up on your fantasy! Now we fuck all the time and while I’m fucking her she’s yelling and telling me how she fucked big black cock all day, how much she loves it, how she takes two cocks at once, how big they are and so on lol…it’s such a turn on! Now I wonder maybe it’s for real, maybe she’s starting to get into it. She even uses the black dildo I bought her on my request. Now I’m fairly well endowed, I’m no small dick cuckold lol. I’m girthy and definitely above average, I just love the idea of a huge black cock railing my gfs pussy! Does anyone know or have any ideas on how I can take this to the next step. I tell her when we fuck how much I want to see her take Big Black Cock so I think she knows…I would like to see if she would try and three some or let me film her with someone but how do I start?