Esther is a pretty complicated character, isn't she? Generally, on the surface, she always expresses animosity and disdain towards Fred, yet on rare occasions, we see that deep down, she genuinely does care about Fred. At the same time, we know she never approved of her sister, Elizabeth, marrying Fred in the first place... so, why did she make such a big deal of Fred's engagement to Donna? I know Donna suggests in one episode that she believes that Esther resents her for seemingly taking Elizabeth's place, but you would think she wouldn't care less what Fred does, or who he decides to be with.
She cares a lot about her nephew Lamont and she even wonders if Donna would be a good mother to him, even though Lamont is well into adulthood. I think it's lets about Donna being a replacement for Elizabeth as Fred's wife but as replacement for Elizabeth as Lamont's mother. Plus, I got the feeling she sees it as cheating on Elizabeth even though she has been dead for a long time. Eventually she gets over not liking Donna and in a later episode she is even mad at Fred when she thinks he is cheating on her.