If your insecurity is so bad that your fiance has to quit the career she has been building in order to appease your feelings... Then "getting over it" isn't really the best advice. "Make an appointment with a therapist" is the best advice someone can give you. And I'm not saying that to be rude or dismissive. I know a girl whose dude had trouble with jealousy. But he didn't want her to quit something that was good for her due to HIS problems. That wasn't what he wanted. He honestly wanted to get help. So he did. Now, she cams and makes money and he is her biggest supporter.
Her quitting camming does not solve the jealousy issue. It really doesn't. All it does is slap a band-aid on the big wound, when really, it needs stitches. On the surface, it might look like everything is fine. But when insecurity is rooted so deeply inside of you, it needs to be addressed. You need to look long and hard about what your real fears. What is making you insecure?
Are you afraid she will leave you for another regular? Does that mean that you are afraid she is only into you for the money, and will move on to a bigger source, should it provide itself? Are you afraid you aren't interesting enough and she will get bored and leave? Even if she quits camming, the root of your fear will be there. And the fear is that she will leave you for someone else. You are afraid of losing her, and even more damning for a soon-to-be-marriage... You don't trust her. Deep in your heart, you don't trust that she will stay. And that is poison to any relationship. That will kill everything before it has a chance to grow into something beautiful.
The thing is... You can't prevent a person from leaving you. Even if she stops camming, she could meet someone at her vanilla job, whom she clicks with and finds herself physically attracted to. She could meet someone in a grocery store. A church. Taking a bus. She can find someone else at any time, and leave you. Is she supposed to give up her normal life too, in order to protect you from your fears? Is she supposed to not work? Not go on errands? Not leave the house in case she runs into someone whom she likes better than you? Of course not. The very idea is ridiculous - as it the idea of asking someone you love to make such a HUGE sacrifice. In any other real world job, asking your partner to quit their lucrative job in order to protect your feelings is absurd. It's dangerously controlling and manipulative and horrifying.
Don't ask her to give up her job because of your insecurities. Don't punish her because you don't trust her. Don't give her a hard time because you can't handle the job that allowed her to meet you. In this line of work, I have literally seen HUNDREDS of girls quit their career because of some insecure dude, who often-times ended up being emotionally-abusive and grossly manipulative. And do you know how many times these dudes actually sought real help for their feelings? Once. All of the others didn't want help. They just wanted their girls to quit, as if they owned their lovers. As if that would solve everything. Expecting them to make a huge sacrifice, as if it was the girlfriend's job to make her boyfriend happy. And I can't think of a single relationship where they both ended up happy. The jealousy remained. The insecurity poisoned them both, just taking different forms in the vanilla world.
If you really want what is best for her, go seek therapy and work with a professional to address your deep-rooted insecurity. Don't rely on her quitting to fix the problems that lurk under the surface. Don't expect her to sacrifice the things she has built, as if it's her job to fix you. It's not her job. It's YOUR job to fix YOUR problems. Which means doing the work, biting the bullet, and going to see a therapist.
Loving someone does not mean punishing them for your unhappiness or fears. Loving someone does not mean forcing them to make huge sacrifices on your behalf, while you do nothing. Loving someone does not mean giving them a hard time while they are just trying to work and pay their bills. Loving someone means you would do anything to resist becoming toxic to their well-being and their life. Your current behavior and thought patterns are very toxic, both to her and yourself. But she can't change it. Only you can.
Sacrificing her job is not going to cure your insecurities and your fears. Punishing her for YOUR feelings is horrible, so please don't do it. She can't fix you. She can't fix your feelings or build your trust. It isn't her responsibility, and frankly, expecting her to do so is deeply unfair. Only you can fix yourself and make it better. Go see a professional who can help you address and heal your thoughts and feelings, and if you cannot get past your issues, then the best thing you can do is let her go. Because you both deserve far better than a relationship filled with poisonous fear and toxic behavior.
Edit to add: Also, stop visiting her room. Stop chatting with her while she is working, stop talking to her regulars, just stop. If it is hurting you and causing your jealousy to flare up, then I know it's hurting her too. If something is burning you, you pull your hand away from the heat, y'know? You don't keep your hand in the flames. Until you can get a handle on your feelings, stop exposing yourself to the thing that hurts you. You said you are getting obsessed, which is dangerous and a little frightening. Getting distance might help clear your head a little and make it easier to handle, until you can talk with a professional.