No. You shouldn't have to give up who you are or what you want out of life any more than she should have to. That's another reason you BOTH really need TIME: time to process, to dig at your feelings of jealousy to find out where they're rooted and determine what it is you actually want and expect out of a relationship rather than just what you're used to being told you should want/expect by the rest of society. Poly may be something you can accept in your relationship, but it may not be. The key right now is you don't and can't know without spending a lot more time thinking about it. It most likely will not take you 14 years to come to a decision- MC and I did no reading at all, we took baby steps and discussed and took baby steps and discussed ad nauseum. But we were already somewhat used to throwing off social conditioning (ex-Catholic and ex-Jehovah's Witness, as well as me identifying as Bisexual) so we knew it was all about what we wanted for ourselves, what worked for our relationships and what would ultimately make/keep us strong. Since we had a common starting point it made everything a LOT easier. There was no dramatic "coming out" because he knew from the very beginning that I was unwilling to limit my connections with others but could keep those connections within certain agreed-upon boundaries for the sake of his comfort.
Back to the point, you get out of this what you get out of any relationship: a partner who loves you and is happy to build a life and future with you. What you need to figure out is if you CAN be happy building that life with someone who also has strong connections to a least one other person. I know that right now you feel like the thought of her being with someone else would tear you apart, and maybe that feeling will last, but maybe it will fade with time, too. I know at the beginning of this journey neither MC nor I ever thought I'd be in TWO committed relationships, but things change. So that's another reason for time. You open up the possibility to adjust and adapt to new ideas.
Let me see if I can get MC over here to give you his perspective, since he's the mono one and there may be more going on in his brain than I can guess at.