I mean she said it herself. The families "skyrocket" in society because they marry good wife's after they abandon trying to marry her because she has been abandoned by the count. So if she isn't abandoned by the count these families might not "skyrocket" either. Same with Sarah, the fact that she is close to the MC now might play a role in the future and make her less important in society so less important in the eyes of the mc too.
But I guess if the MC doesn't try to be close to Sarah and that she become important in society like she was in the previous future but that they aren't close it won't help the MC either. So I guess she might give it a try.