Parenting intervention

My beautiful baby will sleep between 8-9 hours every night. (I am VERY grateful, I know I am lucky and I would never complain). That said, she will not nap during the day. Sure maybe, 20 minutes here or there and typically when I am holding her. Fine if she was an only child and I had nothing to do all day BUT I have a little Tink in this house. I can not trust a Tink to be alone with a baby for even a quick shower. I typically am very ready for a little 'Me time' when Coach returns from work.
This weekend, Coco will be 5 months old. Today, I decided I really needed a shower and it was time for the baby to retire to her crib and 'cry it out'. This would be her first experience with this technique and I would never attempt such a thing if Coach was home.
I placed Coco in her crib, while Tink was engrossed in Max and Ruby. I stood in the hallway.
Not even two minutes had passed before Tink ran into her bedroom screaming...

Tink: I'm commmmming to sabe you, (insert my baby's real name)!!!
Me: She is fine, Tink, she is getting ready for a nap.
Tink: She NEBER go to sleep! She NEBER wants nap. Get her!
I picked baby up to comfort her.
Tink runs to the baby gate at the door, slams it shut locking me in with Coco and herself in the hallway.
Tink points her finger at me and yells: You not get out ob here! You not put Coco in bed! You trap in dere wif her. Be nice!
And she stomped away.

Obviously, Tink has decided that my parenting needs an immediate intervention. If I am not going to take care of her sister to her liking, she will trap me in a room with Coco until I dang well figure out how to do it better.
I soothed Coco and she did sleep in the crib for about 20. Long enough to brush my hair, and apparently it was done according to Tink's approval. I am lucky she doesn't know how to call her Dad on the cell phone.