I would second Sarah's suggestion about the brown sugar. Here it's common to give Rooibos tea with brown sugar to babies/todlers for constipation, it worked really well for my ds. If you would like to try some Rooibos tea, I would be happy to post some too you PM me, ok?

MAYBE, just maybe she already HAS issues with poo'ing at home and that is why she was fine when you visit your aunt, but fell back when you came home?? Maybe she assosiate your bathroom already, they are smart little bugger those almost 2 year olds.

Also I would get a second opinion from another GP, or if possible, get her to a specialist in gastric stuff yourself.

Poor baby. I hope you get this sorted out