I hope that there was genuine affection in these matches and not just political expediency. I'd hate to think that the first "Elendil" of Numenor was a jerk.
What opportunity could a king's daughter have to establish "genuine affection" given the geographical distance? Other than seeing him very occasionaly at some festivals or some general councils she would have no possibility to meet young men regularly enough beyond family or serwants. It is not as if she would go to a mixed high-school or were working at McDonald's in her free time.
Either it would be a "love at first sight" at some random meeting passing each other "in the stairwell" of the palace or a purely dynastic alliance.
Or would we have some jousting festivals where young men from all over the county would perform their knigthly skills in front of a mixed audience?
Remember also that Silmariën is a rational creature - even if she just knows the prospective suitor to be respectable, reliable and not unlikable she might decide to marry him even without being fervently infatuated with him - as being away from the capital and out of the direct control of her parents and later her brother and being the highest noble lady in the whole area might allow her far more freedom and power than if she stayed around.
The issue would be what would cause him to marry her - her status means that she and their future children would always outrank him - this is a position most husbands would generally not like to be in if not outweighed by some other and very solid advantages - political or otherwise.
So e.g. if his position is being challenged by some local rival marrying up would be a solution to that and would consolidate his power. Or if his family is suspect for the throne already then binding himself to it by this marriage would also be a solution.
I do not think replaying the Beren and Luthien story here again would do, we have to save this one for Aragorn and Arwen. So imho it should be a differrent take on the "man-marrying-up" Tolkien trope in this case.
I think this would stress the human side of the story - human do not have the luxury to wait millenia until their fated ideal lover stumbles upon them, they have to learn to love those around them or they "die barren". Silmariën accepting this fact is accepting human limitation deriving from their mortality. She could of course stay umarried if she wanted to but that would mean letting her own line die out.
Working together on the development of Andustar might actually become a common goal they will share - there are few things so consolidating a couple than to share a common goal or passion or loving the same things together...