Rukmani describes her garden in vivid detail in the story. why might she do this? what does this tell readers about how she feels about her garden, and about her character in general?

Using my common sense and a bit of knowledge in English, I can infer that she feels strongly about her garden and loves it very much. This leads me to believe that she is a loving and caring character. If something is described vividly this generally means that 1) this is a good writer 2) they feel strongly about what they are writing 3) both a good writer and a strong feeling. 
Hope this helps!

It could be 1, 2, or 4, depending on the context.1.) they could have had a fight, and she is too humble to say anything further. she wants robert to say something first.2.) maybe he's staring at a computer playing tetris while she's wearing a *really* tight red dress. just sayin' xd3.) is unlikely given that it's only one sentence worth of context long. 4.) it's possible their relationship is more 'mutual hatred' and they tolerate one another.it could be 1, 2, or 4, as long as you can provide sufficient explanation why. remember this as you write!