A domme/sub relationship is a beautiful thing. You wish to serve her. She wishes to dominate you. There's a push-pull that hopefully results in both of you getting exactly what you want.
In most relationships of that nature, there are few things the sub craves more than offering sexual pleasure to the domme, particularly via his tongue. There's something beautifully submissive about it.
After all, your tongue does not experience direct sexual stimulation. Not like your cock. Thus, the act of licking her pussy can be seen as an act of submission. You are offering her pleasure without receiving any, outside of the obvious pleasure that comes from offering your submission, of course.
She knows what you want, what you crave. She can use your desire to tend to her pussy to get what she wants, to make you submit, to make you do something you wouldn't otherwise do. Not all dominant women find that sort of thing pleasurable, but for many that's the point of it. You subdue your desires in order to tend to hers. If you're not willing to do that, is your submission actually worth anything, or are you just using her as a means to achieve your selfish pleasures?
In this case, that latex-clad goddess has a very specific requirement. Like many dominant women, she wants to see her straight submissive cross a boundary that most men of your sexual orientation would never cross by choice. That's the thrill of it for her. That's what makes her pussy wet. That's what she gets off to, including sometimes when she's alone and masturbating to the thought of her loyal submissive swallowing his disgust and wrapping his pretty lips around a cock and sucking it until his mouth is flooded with cum.
Would the pleasure of giving your dominant goddess an orgasm be worth the humiliation and disgust you'd have to suffer through? Would you be willing to be a cocksucker to make her happy? Would you be willing to take a man into your mouth and suck on his dick - while looking up at him, of course - just for the chance to crawl between her beautiful thighs and worship her pussy?
I think most submissive men would be willing to cross that boundary for the right domme. For one that understands how to motivate you, how to convince you that serving her is the highest purpose you will ever pursue. Ultimately, when you become a cocksucker for her you'll be fulfilling both your desires and hers and you'll emerge from the oral experience feeling like a better, stronger, happier submissive. Luckily, she'll give you plenty more opportunities to prove that you're willing to sacrifice your sexuality for her pleasure. And yes, I do mean that she'll have you getting fucked up the ass by a man before too long.
After all, when a submissive man finds a good domme, he'll do literally anything to please her.