it's difficult and time-consuming to check the balance of octopus. i just give her money from time to time, $100-200, and mark in her account book (in and out). i don't care if she will use the actual money or octopus to pay. it's much eaiser.
eg. she needs to take a mini-bus back home. if she is willing to walk up the hill for half an hour and claim from me that $3, i don't mind !!!
Actually I also don't mind if she walk up home or by tram, and claim me back $2. I found that when I let her to buy things at welcome supermarket, the balance at welcome receipt is always difference from her expenses list.
There is also one story in it about using octopus card and that make me to check it whether how she use my octopus card. Because I believe our Octopus system. But there is so many times difference. I just want to know why and I give her octopus card about half year, but actually no one time the balance is matched.
that's why i said: don't check the octopus ! just use a book, mark down in (the money you give her), out (the money she has to spend) and balance. don't spend time on checking the octopus, just make sure her "out" is reasonable. it doesn't matter how she pays, in money or octopus.
you better look into her receipt. why it can be different from her expense list ? how did she explain to you ?