youdontknowme I would say that there is a huge difference between being seen naked by your own sibling or by a random person of the opposite sex. A sibling is not expected to have... umm... "that sort of interest" in her.
Of course, there is a huge difference. As for me I would still feel uncomfortable. My dad is allowed to unlock ad lock me back, but he only sees the waistband
Diana_V I don't see any other option at the moment,
You are better. Just ask her