Dear Mary Beth,
I'll give my reflections on the ending of Shirley by discussing the fates of its two main characters, Shirley and Caroline.
You mentioned that part of Shirley's disappointment in Robert's proposal was because she was probably aware of Caroline's feelings for Robert. I agree with you. Shirley and Caroline know each other quite well by the end of the novel. And Caroline seems to be the only person (other than Shirley) who sees Shirley's feelings for Louis. Caroline tells Robert, in Chapter 35 when he's confessing to his proposal to Shirley, that she thinks Shirley is in love with someone who has not yet made Shirley an offer. Clearly Caroline is referring to Louis. If Caroline can pick up on Shirley's feelings for Louis after such a short time, then surely Shirley is aware of Caroline's feelings for Robert, which have been obvious for the entire novel.
As for Shirley and Louis's relationship, I suppose I see things a bit differently than you do. I don't think Louis sees himself as unworthy of Shirley (at least, no moreso than any Victorian man sees himself as unworthy of the woman he loves); rather, I think Louis is painfully aware of the class/fortune differences between the two, and the likely objection of Shirley's uncle to such a match (and geez, is he right, yikes). Louis always seemed to me to be very self-confident, self-aware, and socially aware, not to mention very intelligent. As for Shirley, I don't see her as giving up her purpose to marry Louis. Sure, she backs off on the running of Fieldhead, as she confesses to Louis after they're married, but I think she did that to give Louis a chance to step up and be seen as her equal by the people at Fieldhead and in the community. I imagine the two of them running the show together before long.
As for Caroline's fate, it reminds me quite a bit of Jane Eyre's. Both women long for more than an ordinary life but end up in seemingly ordinary endings with their husbands. I find both endings a bit difficult to reconcile with the feminist messages that precede them. However, I tell myself that Charlotte Bronte felt the need to give the reader happy endings to sort of sugar-coat her message. At the same time, Robert indicates that he hopes to build up the community around his mill should he continue to be successful, and that Caroline will teach Sunday school, and Caroline and Shirley may someday run a day school for the children of Robert's workers. I think such an arrangement would suit both women particularly well, especially given some of the points you have made about their characters.
Feel free to have another go at the ending of Shirley. There's no such thing as being done discussing something when it comes to Charlotte Bronte! On the other hand, there's also the burning question, what do we read and discuss next? I'll leave the choice up to you!
Your Sincere Friend,