Sticky Situ- Co-caregiver abusing prescription meds, but I need the help

So my sister who helps out with mom and comes up once a week to spend a few nights with her and does lots of odd jobs around her home, etc....has been addictied to pain meds most of her life, sometimes when she over does it it makes her incoherent and or angry when we express concern. My mom doesn't want to ride with her driving, etc. There are often unneccessary little tirades with my sister when my mom confronts her..ok...BIG TEMPER TANTRUMS....but I hesitate to get involved because I NEED the break I get away from being the only other one available to my mom for care most of the time. Is it ethical to let/encourage a sib who over medicates to stay involved? hate to sound selfish but i can't imagine losing the 'help' and time off she gives me.

Sticky Situ- Co-caregiver abusing prescription meds, but I need the help

So my sister who helps out with mom and comes up once a week to spend a few nights with her and does lots of odd jobs around her home, etc....has been addictied to pain meds most of her life, sometimes when she over does it it makes her incoherent and or angry when we express concern. My mom doesn't want to ride with her driving, etc. There are often unneccessary little tirades with my sister when my mom confronts her..ok...BIG TEMPER TANTRUMS....but I hesitate to get involved because I NEED the break I get away from being the only other one available to my mom for care most of the time. Is it ethical to let/encourage a sib who over medicates to stay involved? hate to sound selfish but i can't imagine losing the 'help' and time off she gives me.