@Sash
No, it actually would likely not. If she said everything completely, then it would cause a lot of other issues.
Primarily, the fact that not 1, but 2 girls both are confirmed reincarnated/isekai'd people, and that this world is already one they know about, and that certain possible options exist would creat a lot of trust issues. People would question whether what is happening is their real feelings or just pre-determined actions.
- "Do I love her because she choose a specific path, or do i actually have feelings for her"?
- "Was my future already set in stone without my input"?
- "What else does she know that is this significant, that she is keeping secret"?
- "Is she mentally sane"?
Sadly, the only real way to solve all of this is with time. Even if he says all the right things, all other immediate rivals are dealt with, they make a "promise", its all meaningless. Honestly, she is doing something people normally do; Hypothesizes potential futures and then get worried over them. Reguardless of her previous world knowledge, what she is doing is common, especially in fast and political relationships, which this is both.
Her best option is right in her face, but she cant seem to come to it. That answer is this:
Just don't think too much about it, act normally, dont make an ass out of yourself from jealousy, and just keep to the norm. Maybe make 1 or 2 preventative moves. Anything which builds a consistent, but not annoying or bothersome habit/tradition is best. A good example would be writing eachother short daily love letters. Dont make them overly heavy with emotions, keep them light and simple. Something "easy to read before bed" kind of simple.