Chapter 33: This is letters home to Jo's family, which, for some odd reason includes, specifically, "a young man by the name of Teddy." Seems rather unkind, as she's gone away specifically to give him a chance to fall out of love with her. The sad thing is, she doesn't even know she's toying with him.
Chapter 34: Jo and the Professor get better acquainted. The Professor shows some jealousy toward Laurie's place in Jo's affections. Jo gives up writing sensational stories because they bother her conscience. It doesn't hurt that the Professor doesn't like them and she's sure that Mother and Father would also disapprove.
Chapter 35: Jo returns home, attends Laurie's graduation, then turns him down when he proposes marriage. Laurie decides to go abroad with his grandfather.
While Kate commented on Laurie's behaviors being less than ideal, which some of them are, I don't think that it would be as bad as Jo thinks it would be. Look at her reasons for not marrying him:
I agree with Mother that you and I are not suited to each other, because our quick tempers and strong wills would probably make us very miserable, if were so foolish as to --" ...
"Marry - no, we shouldn't!" If you loved me, Jo, I should be a perfect saint, for you could make me anything you like."
"No, I can't. I tried it and failed, and I won't risk our happiness by such a serious experiment. We don't agree and we never shall, so we'll be good friends all our lives, but we won't go and do anything rash."
Thing is, Jo has been able to influence Laurie, and he's influenced her. The fact that she wants to "be good friends all our lives" says to me that there's more to her feelings than she's allowing herself to see. Instead of asking herself what life would look like without him, she's acting based on fear that things won't be perfect. She's repeating the things her Mother said (which I still maintain was really bad advice) because she's afraid of getting married, afraid to change, and afraid of not being good enough. Look at what she says a little later:
"I'm homely and awkward and odd and old, and you'd be ashamed of me, and we should quarrel ... and I shouldn't like elegant society and you would, and you'd hate my scribbling, and I couldn't get on without it, and we should be unhappy, and wish we hadn't done it, and everything would be horrid!"
The problem isn't really Laurie at all, the problem is within Jo herself. What Laurie should have done is keep up with the changes that he's made, and see how they fit over the long term. Really, is longer hair that big of a deal? As changes go, that one seems rather trivial. Playing billiards also seems like a pretty little thing. The other change he seems to have made is working harder than before. While this is a bigger deal, I don't see the harm in bettering yourself, regardless of the cause. What Laurie lacks, and I think the thing that really costs him the girl in the end, is patience. He should never have proposed when he knew she was going to say no! He should have invited her to do fun things with him, to spend time with him. He should have made himself indispensable to her, and given her time to see that marriage, based on a good friendship like theirs, could be a wonderful and beautiful thing. Who knows what a year of learning his grandfather's business and continued friendship might have done for him. But instead of waiting for a better time, he forced her to tell him that she didn't want to marry, and thus dashed his hopes. I think that Jo herself realized, at the very end of the chapter, that it was the end of something special:
Ah, but it wasn't all right, and Jo did mind, for while the curly head lay on her arm a minute after her hard answer, she felt as if she had stabbed her dearest friend, and when he left her without a look behind him, she knew the boy Laurie never would come again.