Re LW2, the minute sibs show up with nibs in tow without warning, she needs to leave the house whether she has a social engagement or not. Sibs need to realize LW is not their on-call babysitter and LW is not accountable to them. (I bet LW is also unpaid for her labour.) Sibs' lack of planning on their part is not an emergency on LW's. When they ask LW whether her social engagements are more important, LW should say yes and that's not negotiable.

(This applies to LW's mom too. If Mom wants to babysit, that's her prerogative, but LW must not get involved if she doesn't want to babysit.)