Just when I was about to tell you that, no, marshmallow pasta is not an option ... you admit you actually like the inside of the onion rings too. There's hope for you yet, kid!
So, first off, you need to revise your "I don't like onions" statement because it's not true. Evidently you don't like some onions, and so far it appears that cooked onions might possibly land on your "yes" list. Is it raw ones you don't like?
If you like the insides of onion rings, one day please, just for me, take an onion and slice it and plunk it in a pan with either olive oil or butter, turn the heat on as low as possible, and let it cook for a half hour. Turn it occasionally, but otherwise just wait until it's golden brown, very soft and limp, and reduced greatly in size. Pull a bit out and try it -- is it sweet? Is it more like the insides of onion rings?
As for your girlfriend and her mother, sigh ... mostly I feel sorry that her mother decided to indulge her this way because I honestly, with all my heart, think that she's missing out on so many wonderful foods by having been allowed to get so picky. Still, while I'm grateful I was raised not being allowed to refuse ANY food (could only have a "no-thank-you serving" which I had to eat) and maybe because of it as an adult I'm open to almost any food (bugs excepted) ... as a mother I have to admit it can be easier said than done. My son who's almost your age will try almost anything but my younger daughter turns up her nose and refuses point-blank, and I'd swear they were raised the same way ...
Anyways! You're only 18 and it's really promising that you're hanging out on this site. That means the interest is there and that's the most important part. Now if you'd just try to open up a wee bit more to new flavors ...?