Hmmm... Picky eater. Mine's picky with greens/veggies, but hoovers anything that moves. They're all different, and it behooves us to learn their individual idiosyncrasies.
I wouldn't (normally) expect her to defecate until 24-48 hrs. after eating well, so if she went a few days w/o eating, I'd expect a few days w/o the other. The weight gain is encouraging; I'd be concerned if she were losing that much weight over the same period. Once she levels off (stops growing naturally) I'd start thinking about weight gain/loss in terms of percentage of total body weight rather than X grams. I don't remember the threshold OTTOMH, but I'll ask next time I see one of the vets.