An update on my sister's situation:
She managed to land herself in quite a trouble. Basically, like mentioned here previously, it's possible to take the bands off your thighs if they aren't connected with a crotch chain. Well, she managed to convince my father to remove the crotch chain (I bet you all see where this is going). A couple of weeks go by and, one morning, mom catches her folding her thighs out of the bands.
I actually warned that she'll get caught but to no avail. Basically, now she has to wear the blocking piece at night and a crotch chain, and the crotch chain will be in place for the day as well. As you can imagine, she isn't very happy about this but she knows she deserves it