Rebbitzen- “Seeing what other Yidden are doing and following their precedent is accepted in Yiddishkeit.”
Again, the example you give is misleading. All that Gemara stands to prove is that when originally establishing the Halacha and approached with a valid Halachik argument, the dictation of correct Halacha followed a social tide. Once Halacha is Kavuah, that is not the case.
This is also the rebuttal to Louis Ginzburg’s argument for Conservative Judaism based on the Gemara in Avodah Zarah in regards to shemen Akum. Once a Halacha is established, precedent to veer away from said halacha is insignificant.
That being said, it should seem obvious that a Shidduch between these two different worlds is a bad idea. Their unique perspectives about Halacha are, at least on an idealistic level, rooted in their perspective about the world. Now, obviously two individuals who decide to get married should be different and compliment one another. However, all with the understanding that they have a common ground in regards to perspective about the world and where their lives are headed.