@Oeconomist
By Aki I assume you made a mistake and are referring to Yuumi's friend (who wasn't named).
While ideally, you'd hope never to associate with people who make assuming and rather insensitive remarks in the first place; realistically you can't avoid such instances in life and I think Yuumi handled it very well.
Just like how opinionated her friend is, there is no need to go to the extremes either to disparage her friend's remarks and force her friend to conform to the notion that Kanata is suitable for Yuumi. In the end, it is a subjective opinion from someone who doesn't know Kanata in person, rather than someone who is familiar and despite being able to see for themselves, yet still holds that prejudiced notion. Therefore, it is Yuumi's role to convince her friend of Kanata's 'suitability', should she value their friendship.
More straightforwardly you can break it down to weighing their friendship against her friend's presumptuous attitude, and in most cases, I think people are magnanimous enough to overlook some presumptuous attitude.
Rambling on a bit, but this is a really intriguing insight into relations. Call it insincere as you will, but most people in society tend to withhold negative opinions themselves and imply it through subtleties which protects you from unwanted conflict/loss (consciously or subconsciously). In this case, it would be that Yuumi managed to maintain a relationship with her friend which could benefit her (who knows? maybe you need the connection sometime later down the line or they might be able to provide an opportunity) with no immediate loss - as her friend doesn't know Kanata and therefore there is little to no chance that Kanata would hold it against Yuumi for not breaking ties with her friend.
Even more of a tangent - at the other extreme people are lulled into escapism through this mentality, by staying silent in so many cases when faced with difficult decisions; even when sometimes a definite stance is necessary and wholly lacking, especially in the political landscape of most developed western democracies.