We had the same situation - She first refusing, then over time, not agreeing but no longer outright refusing yet still not ever discussing it. I'm cutting and pasting a post I made last year regarding how it finally came to pass. I hope you find it helpful.
"My Wife's first experience was with a BBC - "office sex" in a way. She was in her mid 40's and we were at a Holiday Office party (her work)the evening of a work day. I was never really able to satisfy her and we'd always discussed the idea of her being fulfilled by a larger cock and naturally the BBC mystique entered into the discussion. At this party after a good deal of drinks, the opportunity arose with a black co-worker of hers. She had an excessive amount of drinks, and we began chatting with the co-worker. I steered the conversation with subtle sexual innuendo's and he easily caught on and indicated agreement. It was getting late, and some of the other people were beginning to leave the restaurant. We moved over to the bar/lounge section of the restaurant, which was pretty dark and empty (though still open) and took a booth which was pretty secluded and ordered more drinks. Once the drinks came and the waitress left, I started rubbing her tits. She didn't object to being felt up in front of him, nor did she object when I invited him to feel her up. In short time, I suggested she give him a hand job. In the privacy of a booth, she began stroking him while I opened her blouse and played with her tits. He unzipped and she had him in her hand stroking and pumping, and, to both his and my surprise, she bent down and began sucking his cock and kept at it until completion. No one actually saw her sucking his dick, but several of her co-workers figured out what we had done. When the party finally broke up, we stayed a while, brought her into the men's room, locked the door and she blew him again. Eventually, they fucked, and she's had many others since then, but she still gives him and several of her other black co-workers blowjobs on a regular basis.
