Thanks. I agree with the idea, but I think in details we view it differently.
Month Ji and Day Ji can be viewed as seperate entities, sure, as Month is outside, showing people nearby etc.
While Ji in the month will be stronger.
Puppylove used to use the idea that in some situations the DM can "extend".
We can look at the branch, if the 2 branches are connected(in this case You and Si, the definition of this kind of connection wasn't clear enough but I assume Si being birth place of You may suffice). Basically the idea is both Ji will show the DM, the person sees themselves as an influence in people nearby as well, extending to beyond the usual area Day Pillar reaches.
We(in other forums) had charts of people that have the same pillar in hour, day and month and it did seem that the effect was much closer to the DM pillar extending and seeing itself in everyone else, while the people around see them as not recognizing the separation.
So while I can't say this isn't the case, I have doubts that we can be sure Ji in month and Ji in day are separate entities. If they are I would agree with this part, however.
The other aspect I was mostly focused on before was the Si in the month.
As we have You<>Si combination, and while the stems may show DM, the Si seems to be something else. Parent can show a marriage certificate as we have used often and the combination with the month in this way can show a relationship.
While sometimes there is hesitation in using Resource to show the spouse star, while Si may also fall in Xu, or the connection of Si to Xu and the harm between Xu and You may create tension(with his friends), in general I would view it as potential relationship that may become marriage and can even be stable with some crafty maneuvers(holding against the chart when the fact Si originates from Xu may relate it to the harm etc.).
I do agree the interactions in the stems if we view them as different entities(one Ji as DM, one as friends/competitors) will very likely lead to what you are saying, yes. On the surface, however, so right after she meet someone older someone nearby may combine with him instead. I'm not sure they are separate, however and I also think there are still chances with the Month Pillar and the Si there as the spouse palace is healthy enough and there are good strong Images of stable relationship, if they play it right.