As with many men and resistance to oral sex, the cause for women is most often negative childhood conditioning. In our culture little girls receive both subtle and overt religious disdain for genitalia and fear-based ideas about the penis. In addition to this and equally serious is the negative impact of infant and child sex abuse by older males. Statistics show 2 out of 5 young girls get sexually molested. Many repress the painful memories to such a degree that they become women with "unexplainable" sexual fears. Much healing may need to take place in order to create the inner safety that allows love to blossom and energy to really flow.
Tantra can definitely help. For a woman to observe another woman lovingly and enthusiastically orally pleasuring her man can begin to offer new possibilities. I recommend that women who don't like giving oral sex watch the video "Ancient Secrets of Sexual Ecstasy" Watch it several times with no males present and open your mind and heart to embrace the experience of the women in the film. Remember to breathe and feel your deeper feelings if necessary. In addition, spend time with ancient Tantric sexual paintings from China and India and flood your subconscious with images of lovemaking that is obviously based upon reverence of male and female bodies, hearts, and souls.
Lastly, through the study and practice of Tantra and associated energy arts (Chi Kung, Tai Chi, Reiki, massage, yoga, Aikido, etc.) a woman (or man) can develop both a sensitivity to energy and a capability for commanding energy, as well as an enthusiasm for playing with energy. Few living things in our culture have as much energy as an erect penis (or engorged clitoris), and certainly the mouth, lips, and tongue are among our most prime tools for sensing, enjoying and becoming aroused by energy. It's a match made in heaven!
PS This applies equally to men giving oral pleasuring to women! It's all about the relationship between energy and pleasure!