Then they get hormonal and moody with pregnancy. Bored later on, and generally difficult.
Unless she has a strong focus instilled into her from her trad family background she will be almost certainly difficult to deal with no matter how well you "get along".
So what you should look for is a strong traditional background.
A family that are neither too wordly nor mad with bizarre theories.
You brought up some good points there.
Not just "how good of a Trad is she" but how CONSERVATIVE was her upbringing in general?
I've seen plenty of long-time SSPX attendees be LOUSY with liberalism, feminism, and worldliness -- meanwhile I've seen converts and "converts to Tradition" who are genuine, true-blue Trads who are integrally Catholic (Catholic 24/7) and who really live the Faith.
I think it has more to do with their culture -- how they were brought up -- than any adherence to Tradition that was added some time later.
But also there are going to be some challenges, etc. with just about anyone you marry. The question is: Are you equipped to be mature about it and deal with those challenges well, when the time comes?
Are you good at communicating, controlling your emotions, have a FIRM and unshakable foundation in Fearing the Lord, etc. That is the sine qua non, the dealbreaker, when deciding to get married.
You also touched on the point of WHY does she believe stuff, not just WHAT does she believe. A woman who believes a truth accidentally (because she FEELS its right) is worse than a woman who holds an error while doing everything right (she had the right thought process, she was trying, but happened to be wrong because she missed something).
As Our Lord said, "Judge not according to appearances, but judge just judgement." You have to look deeper.
Look at all the SSPX Catholics who (turns out!) weren't there for the right reason -- just there for convenience, socializing, popularity, etc. Meanwhile, there could be a good conservative Catholic attending the Novus Ordo because she hasn't found anything better yet, but her LIFESTYLE is actually more Trad than many of the Trads warming the pews in the SSPX!
Again, you have to look at the individual, and not just judge books by their covers.
An interesting topic for discussion!