@OnlyTruth
If you are dare to say that you "love" someone it already implies that you are wanting to be in a lifelong relationship with that person. If not, you don't have the right to say these words.
Love is simultaneously the only one true union and the most fiercest fight that can be.
You are calling her "crazy" and "psychotic" only because you see her panicking about the things she doesn't know. If you share everything with her this misunderstandings will become obsolete, cause there is no reason for her to worry, she will already know that he is hers, and she is his.
On the other hand you need to demand all of the above from your partner. This must be done by any means (in the majority this means are "wholesome" and "cute" interactions like threatening a kiss to extract needed information) to establish indestructible whole-hearted union that is called "Love".
If you are not willing to take this risk, all of your commotion is just a child's play.
These "yanderes" that we are talking about is the most furious and powerful warriors of love that can be. You either unified as one in your own little world alone or you get obliterated because of your selfishness and indecisiveness towards your, presumable, one and only.
It is like wielding double edged sword. If you know everything about your weapon, you are unstoppable, if not, you just cut yourself and bleed to death.
Do or die situation. Be the happiest man in the world or die as puny indecisive garbage/cheating scum (two of the most common reasons to fail in my opinion).
I think yanderes can help anyone become one of the more admirable, dignified people. (Or crazy chaotic sweeping storm of a couple, sometimes both).