I guess I am wondering how she feels that she is protecting people's feelings by hiding her poly side. To me, that is a big lie because it sounds like cheating to an extent. Correct me if I am wrong. If the boyfriends do not know that there are others, how is that fair to them? It sounds like she not only wants a slice of the cake. She wants the whole thing and be able to eat it. How is she hiding it? Is she telling him/them that you or the others are just friends?
I never want to have to wonder if someone I love is telling me the truth, so even lies of omission would not sit well with me. One lie leads to many lies because that person has to keep covering them. Then, the breakdown of trust begins. I would wonder what other lies were being told.
And while it is a long-distance relationship, I would suggest not putting a time limit on it. Like saying that once your children get older, you may not be that into it. If someone were to say that to me, I would have to tell them that I am not for lease or rent like a leasehold property/island that you only own/borrow for a given amount of time. Yes, relationships change. It sounds like you are expecting the end before you even reach that point. You may very well decide in six months or a year that you do not wish to continue having an online/long-distance relationship. She may decide that she wants to live closer to you. Who knows? You live in the moment, but you do not worry about the end when it is just the beginning. That is the wrong attitude and approach. I understand being a realist, but that thought can be a nagging presence that could cause you problems. Try to let it go and enjoy what you have.