This is kind of silly. Wellesley and Barnard are of equivalent academic quality and prestige. Anyone who thinks otherwise because of comparing admit rates or trying to draw some sort of adverse inference because of Barnard’s partnership with Columbia is just grasping at straws. Anyone who tells the OP to pick one of the other because of rankings is wasting her time.
The OP raised questions about campus environment and in those areas the schools are quite different. Urban vs. suburban; unitary college campus vs. a school that is physically and geographically tied to a another campus; a true all women environment compared to a hybrid single gender/ coed environment – and probably a variety of other differences in campus culture that might be apparent to people who have spent time on both campuses.
However, the OP hasn’t been back. If I were in her shoes I would be frustrated that this thread has devolved into yet another Barnard/Columbia debate rather than answer her questions about modern language departments or community/social scene.
I guess the only part relevant is her question is that Columbia/Barnard community/social scene is essentially identical There are a few Barnard-only traditions, and Barnard has its own dorms-- so the Barnard student’s experience will differ from the Columbia student’s experience to that extent. But beyond that students with common interests on either side of the street are going to probably end up participating in similar activities and socializing in similar venues.
Columbia has fraternities & sororities, so to the extent that a prospective student is interested in that social scene, that is another differentiating factor from Wellesley. (My daughter’s concept of socializing did not include frat parties and she had no interest in joining a sorority, so I can’t provide any more information beyond the fact that they exist.)