I have never liked the term soul mates. Its inherently limiting. About 15 years ago...give or take, I found a term that stuck. Soul Friends...or in its original term - anam cara. In its simplest form it allows us to have a soulful connection to more than one person for more than one reason.
I truly believe in this term and it has been proven time and again. People come into my life that impact my soul to its core. Soul Mates is just such a limitation on a potention thought
As to your specific challenges. All you can do is keep talking and educating yourselves. The only way to make it work is start the process. Explain whats happening and point her in directions to learn at her own pace. You can't rush it, if you do, you may end up hurting her more than necessary. You need to figure out if you BOTH can do poly before you jump in feet first. If not, you may need to look at another configuration than a triad
You, should also look up NRE. Read up on it in detail. You may find some insight into what you are feeling. It reads a lot like NRE has you full in its grasp.
Best of luck.