There is no guarantee any marriage based on any set of values will be an improvement over spinsterhood or even a successful marriage for that matter. I will concede there were plenty of miserable spouses but Charlotte does not think she will be one of them. What evidence do you have that Mr. Collin’s will make Charlotte’s life miserable? Charlotte is not yet married to Mr. Collins in Chapter 25 and he has not revealed himself to be a dishonest, cruel, irritating husband. So far Mr. Collins has certainly proved to be an irritating fiancé which bodes for more of the same later but I do not see where you perceive cruelty from his actions so far. I think it was dishonest of him to accept the return invitation to Longbourn in Chapter 22 since by Charlotte’s request he withheld the fact they are engaged. Charlotte knows all of this and wants to marry him anyway.

I think it is also worth considering that Charlotte’s unromantic nature is a great asset to her in successfully combating Mr. Collins’ faults. She has already shown skill in manipulating him to propose and be happy about it; she even prevented him from gloating to the Bennet family on “his” success with her. Many people are irritated by, dishonest and cruel to their spouse and that is true for marriages which begin with esteem and respect between both partners—indeed in JA’s era they are just as much trapped as those who do not if things turn out badly. Although Charlotte’s views on marriage and men are quite pessimistic by my standards but she is right that people change and not always for the better.