hi...
i actually had this same problem before; as a matter of fact, sometimes i still do. some women thinks that certain sexual acts are "naughty" and "dirty". these are the women who would like to always be considered a lady and nothing less; however, in actuality, they sometimes love and enjoy these "naughty" and "dirty" acts (but they don't like to admit it, for fear of being considered something less of a lady).
talk to her and let her know that what goes on between you two is your business, nobody else. so you two are free to do any and everything to and with each other (so long as you both agree)... let her know that you won't see her any differently than the sexy "lady" that you married.
what you have to do is make her feel relax, comfortable and sexy. you can probably set the mood: start of with a nice bubble bath (that way she can feel confident in knowing that she's clean. some women are afraid of how they may smell down there); dim lights; slow music... etc. you pretty much have to perform a considerable amount of foreplay, to allow her to feel relax, comfortable, sexy and ready. let your eyes tell her that she's the most sexiest person in the world. place soft sweet kisses all over her body... and that's when you place kisses up her thighs and higher... but don't rush right into the oral sex... you just need to tease her with sweet kisses in that area. continue to reassure her that she's beautiful, she's sexy and that you want to experience a new level of ecstasy (while you're continuing to tease her with sweet kisses.
at some point, you can sneak your tongue in, to tease her clit. if she tries to stop you, make it seem as though you're begging her "not to deny herself the pleasure"... tell her to embrace it and enjoy it, because you're just focusing on her.
sometimes, my wife still says that it feels as though we were "dirty"... but in the end, she's able to reach a wonderful orgasm, have a peaceful and wonderful night's sleep, and wake up with a smile. it's worth it.
i hope all goes well with you.