] I also wonder if she wanted Jane not to think ill of Darcy at that point?

In Chapter 37, Elizabeth's own feelings about Darcy are described as follows:

she could not approve him; nor could she for a moment repent her refusal, or feel the slightest inclination ever to see him again.

I don't think she worried about Jane's opinion of Darcy. But she did know that mentioning Darcy's interference in the Bingley-Jane relationship would just cause Jane more pain, and there was no need to tell. It was something that Elizabeth would have loved to share, I think, but not at that cost.