Why not try the 69 position next time you go down on her, she may not suck your dick initially but with a little encouragement she may start, at first she might not be able to give you a proper blowjob but in time you could get her to go ontop so she can.
Are you clean? You may think you are but it's always a good idea to freshen yourself up before sex even with your wife, she can think you stink the same way an escort can. A lot of ladies don't like sucking dick thats after been inside them so how is your timing, are you pulling him out then expecting her to suck on him? These are just things to consider, maybe you are doing all the above already but at the end of the day if she doesn't like it other than gentle persuasion there's feck all you can do about it, the getting huffy with her approach is never going to work on a woman..