I'm not huge into bjs (don't get me wrong I like them but I'd much rather give her the high hard one) but a woman who refuses to even attempt oral sex rubs me the wrong way. I interpret that as a sign of a sexually selfish woman. If you're girlfriend is holding out on sucking you off, it may take a little effort to bring her around. She probably hasn't done it before, or she has done on a few occassions but had a bad experience with it. The most common female fears about oral sex:
You will ejaculate in her mouth
She will be terrible at it and embarrass herself
She does not like the idea of her mouth on the organ you also use to urinate
She will gag and vomit on you
Some of these are reasonable("I'll tell you when I'm going to come" ranks up there with "The checks in the mail"
but you're going to need to quell her anxiety. Don't heavily pressure her, but let her know that you would really appreciate it if she did gobble your nob. Try and introduce it as foreplay. She probably will be more willing if its in the context of a playful mood than an intense sexual activity.
Be sure to let her know your enjoying it--moan a little, tell her you like the way it feels-- and tell her how sexy and sensual she looked while performing.Reassure her that you have no intention of coming in her mouth. Tell her you don't care about her swallowing (alot of women are under the impression that we expect them to do just that)
Also, make it known to her that its not required for her to take your entire penis into her mouth or for her to "deep throat" you. If necessary, show her exactly where your most sensitive and would like her to put her mouth and tounge. A surprising number of otherwise experienced women don't really know what parts of the male genitalia are most sensitive to the touch.
If she absolutely refuses, go on strike! lol Refuse to go down on her until she reciprocates. Seriously, it worked for me once, though I suppose it could lead to hard feelings. I think whether or not refusal to blow is grounds for a nexting is a personal choice, but if she can't be troubled to sastify your sexual desires, how good of partner can she be?