I agree with a lot of posters here - don't give up, but don't pressure her either.
Maybe a different approach... start off with lowering her inhibitions. Ask her to start sending you naughty pics. Then maybe, throw around some role-playing about having a 3rd in the bedroom... throw in some dirty talk. Ask her what celebrities she finds attractive... if she would fuck them, given the chance. Just toss it around, now and again.
By the way Tara, those are some scorching hot pics of you taking all that BBC meat. Your are one dirty, filthy cuckoldress... a cuck's dream cum true. I think we'd all like to see more of you worshipping those stallion cocks. Show us more.