al-che,
if you can't stop her then join her. i don't mean you join her sa pag suyop but rather you join her in her session with your siblings f naa. later on she will realize how bad she is doing and how badly she is needed by her family.
and of course show some affection to her kay basig ksp nana ron kay d na love sa imong dad or perhaps wala na pud mo ka bonding --- assumptions lang ni ako ha.
most importantly, don't stop on praying kay prayers can move mountains.