I certainly will agree with you that insult and moral outrage would be part of Rand's emotional package in responding to being rejected by a man she loved.
To me, that part has two components, though. I am not talking about jealousy here. Merely insult and moral outrage.
1. The first is precisely the sense you mention (which I am presuming - so please tell me if I got this wrong): an emotional reaction based on conscious programming, just like Rand laid out in her writings. She consciously identified her ethics and programmed her subconscious with them. According to her ethics, her own highest value choosing an equivalent (to her) of a shop girl would be highly insulting and prompt moral outrage, regardless of whether she was replaced by this or not.
2. The second part, one not so much under her control, belongs to the another part of the mind I don't find discussed too much in Rand's writings. All great artists I have personally been near have this - and I usually find it in written accounts of the great.
There is a sort of centering the world on their own existence in an almost childlike manner. It is more of a conceit or self-absorption than rational selfishness - a narrowing of the world's problems and all the contexts of others to the small universe of their own personal affairs. Rand got near that issue with the "world will end when I do" sentiment, but that is all I remember.
Without such a high sense of self-importance in the overall scheme of things, a person does not have the emotional "fuel" needed to become great. I know of no great person where this is absent. (Yet the world does go on without any particular one of us.)
Also, great people (the ones I have known) tend to be very controlling of their intimates. The descriptions of Rand in this sense that I have read show her to be extremely similar to what I have seen up close in other greats. I believe that this "childlike" facet of selfishness is the reason for this.
From that view, the rejection of a world where earth-shattering events are occurring (which happens to be the artist's own world) is extremely insulting. It is a negation of the obvious and it is disgusting to them.
Rand's documented reaction to Branden's rejection is so similar to what I have witnessed in others that I have no reason to believe that she was immune to this automatic drive to excel and become the center of the universe within herself.
From there I would add jealousy. However, I also believe that Rand would be perplexed by the emotion itself and actually not know what it was unless she pondered it introspectively.
This is something that actually happened to me in my thirties. I have no recollection of having felt jealousy up to that point except for some memories about my brother when I was very young. All of a sudden I found myself acting strangely with a woman at that time. Often, I did not recognize myself - and I did many strange things that were out of character for me. Fortunately I was able to introspect enough to understand that I was becoming jealous. (Still, a fat lot of good that did! - LOLOLOLOL... Maybe I'll tell the story someday.) I have rarely felt that emotion since then. I know how it feels and it is horrible. When I sense it coming on, I take immediate steps to halt whatever is causing it.
All this makes me look at Ayn Rand as a human being who was very much subject to human emotions. She just had the added context of being one of the greats, with an internal emotional make-up that is very typical to what I have seen, and furthermore the added context of a conscious programming her subconscious (to the extent that it can be programmed) with her ethics - exalted ethics, by the way.
As you can see, I do not believe in simple equations for human behavior. The human being is a complex animal and I sincerely believe that Ayn Rand was complex, too.
A strong conviction of this complexity - and a driving need to understand it - is part of my almost violent rejection of the viewpoint of people who say that Rand was not jealous, was perfect (morally or otherwise), and whatnot. I detest the oversimplification of great lives. It is a bane on a proper understanding of them and of life in general.