Oak, the answer here is really simple, if you are really into this girl and expect to spend time with her, give up on blowjobs. If blowjobs are a high priority on your scale of sexual activities then find a new girlfriend who enjoys both giving and receiving oral. The women are out there, dear.
EDIT: The rest of this stuff is sort of stream of consciousness about dating behavior vis a vis neuroendocrinology and its impact on the brain in regards to both long and short term relationship behavior. Don't read it if my longwinded rambles bore you (you know who you are). You have been warned.
When we first fall into heavy infatuation (you know that feeling of walking on clouds all day, having no appetite, your heart leaping at just the sound of your beloved's name, you can't wait to see him/her again, you spend 10 minutes saying goodbye on the phone, etc., etc., etc.) both women and men will do more shit they don't necessarily love to amuse or please their new s/o. And NO, it's generally not an issue of deceit, it's more that whole first flush of infatuation creating high dopamine and norepinephrine levels and low serotonin levels, all of which in turn create a higher willingness to experiment. How many times have you heard about a chick saying to a guy "I've never done this before" or "I've never wanted to try this before." You cynics out there think they're lying and some of them are, but generally it's hormones! Very often that wonderfully new and in love endocrine system has more natural shit flowing through people's brains than your average attendee of a rave (science has proven this). This feeling eventually drops off and that's why there are people who serially fall in love. They are hooked on that first flush feeling of being infatuated and it can be intoxicating and addictive.
Over time, the more secure you become in the relationship the hormones change, you develop feelings less of romantic love and lust and more of attachment and comfort driven by oxytocin and vasopressin. Now your logical brain starts to engage a little more, and you start editing out the stuff you really struggle to do (holding in farts, brushing your teeth multiple times a day, wearing super sexy underwear all the time, taking a dump anywhere within proximity of your s/o).
There's actually a biological reason for all of this ... it has to do with perpetuation of the species. Theoretically, you've created a child by the time the first flush of romance wears off and now the focus of the relationship needs to become more about day to day survival and protection of the young and less about doing it like bunnies. If we stayed in a habitual state of dopamine driven ecstasy all we'd do is fuck and never plan for the future.
So when you're in a committed relationship you actually end up with a list of "I ain't fucking doing that shit no more." For men the list has a tendency to revolve around areas of personal hygiene and/or etiquette whereas for women the list is often heavily focused on sexual acts and general levels of tolerance for bullshit.
Why do you think marriage is hard? Sometimes you have to REALLY WORK to remind yourself that you really and truly DO love that miserable pain in the ass who is sitting across from you at the dinner table and by god you're going to keep this marriage together even if it means you're both hanging onto it like grim death.
The truth is one of the main reasons people manage to make a relationship last is less because of the things they have in common but more because they found the person whose annoying traits they find least offensive.
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