Physical intimacy is an important part of romantic relationships, IMO. Is it possible to carry on a romantic relationship without it? Yes, but I have to imagine it's less fulfilling, particularly to you since you are the one who seems to need it. Without it, you're somewhere between friend and girlfriend. Or, like a girlfriend who's saving herself for marriage. Except, there isn't actually the goal at the end.
Maybe you two are having sex once a month, but sounds like obligation on her side rather than enjoyment. To be quite honest, I wouldn't want obligation sex. Would make me feel like crap.
Instead of discussing your need for sex with her, you could try discussing why she doesn't seem to have a need for sex, because not having that urge is unnatural (probably don't call her that lol). It could be she has that hormone issue due to genetics. Or, it could be medication she's on, or her diet, or her lifestyle. Or a combination. Waiting for a medical solution is probably the wrong way to go about it. If she wants to have a long term relationship with you, she should be making the effort to try things to alleviate the issue that is driving a wedge between you. I know you say you feel like soulmates, and you're being supportive, but this absolutely is a wedge between the two of you. If she decides she doesn't want to make the effort to bond you two closer, then you have to decide if you want to live a sexless life with the woman you love (the prospects for sexlife only diminish with age), if you can satisfy your needs elsewhere while staying with her, or if you want to try finding someone who reciprocates your needs.